#ifndef DATE_H
#define DATE_H

// The MIT License (MIT)
//
// Copyright (c) 2015, 2016, 2017 Howard Hinnant
// Copyright (c) 2016 Adrian Colomitchi
// Copyright (c) 2017 Florian Dang
// Copyright (c) 2017 Paul Thompson
// Copyright (c) 2018 Tomasz Kamiński
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// Our apologies.  When the previous paragraph was written, lowercase had not yet
// been invented (that would involve another several millennia of evolution).
// We did not mean to shout.

#ifndef HAS_STRING_VIEW
#if __cplusplus >= 201703
#define HAS_STRING_VIEW 1
#else
#define HAS_STRING_VIEW 0
#endif
#endif // HAS_STRING_VIEW

#include <algorithm>
#include <cassert>
#include <cctype>
#include <chrono>
#include <climits>
#if !(__cplusplus >= 201402)
#include <cmath>
#endif
#include <cstddef>
#include <cstdint>
#include <cstdlib>
#include <ctime>
#include <ios>
#include <istream>
#include <iterator>
#include <limits>
#include <locale>
#include <memory>
#include <ostream>
#include <ratio>
#include <sstream>
#include <stdexcept>
#include <string>
#if HAS_STRING_VIEW
#include <string_view>
#endif
#include <type_traits>
#include <utility>

#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
#if __GNUC__ < 5
// GCC 4.9 Bug 61489 Wrong warning with -Wmissing-field-initializers
#pragma GCC diagnostic ignored "-Wmissing-field-initializers"
#endif
#endif

namespace date {

//---------------+
// Configuration |
//---------------+

#ifndef ONLY_C_LOCALE
#define ONLY_C_LOCALE 0
#endif

#if defined(_MSC_VER) && (!defined(__clang__) || (_MSC_VER < 1910))
// MSVC
#define _SILENCE_CXX17_UNCAUGHT_EXCEPTION_DEPRECATION_WARNING
#if _MSC_VER < 1910
//   before VS2017
#define CONSTDATA const
#define CONSTCD11
#define CONSTCD14
#define NOEXCEPT _NOEXCEPT
#else
//   VS2017 and later
#define CONSTDATA constexpr const
#define CONSTCD11 constexpr
#define CONSTCD14 constexpr
#define NOEXCEPT noexcept
#endif

#elif defined(__SUNPRO_CC) && __SUNPRO_CC <= 0x5150
// Oracle Developer Studio 12.6 and earlier
#define CONSTDATA constexpr const
#define CONSTCD11 constexpr
#define CONSTCD14
#define NOEXCEPT noexcept

#elif __cplusplus >= 201402
// C++14
#define CONSTDATA constexpr const
#define CONSTCD11 constexpr
#define CONSTCD14 constexpr
#define NOEXCEPT noexcept
#else
// C++11
#define CONSTDATA constexpr const
#define CONSTCD11 constexpr
#define CONSTCD14
#define NOEXCEPT noexcept
#endif

#ifndef HAS_VOID_T
#if __cplusplus >= 201703
#define HAS_VOID_T 1
#else
#define HAS_VOID_T 0
#endif
#endif // HAS_VOID_T

// Protect from Oracle sun macro
#ifdef sun
#undef sun
#endif

//-----------+
// Interface |
//-----------+

// durations

using days = std::chrono::duration<int, std::ratio_multiply<std::ratio<24>, std::chrono::hours::period>>;

using weeks = std::chrono::duration<int, std::ratio_multiply<std::ratio<7>, days::period>>;

using years = std::chrono::duration<int, std::ratio_multiply<std::ratio<146097, 400>, days::period>>;

using months = std::chrono::duration<int, std::ratio_divide<years::period, std::ratio<12>>>;

// time_point

template <class Duration>
using sys_time = std::chrono::time_point<std::chrono::system_clock, Duration>;

using sys_days = sys_time<days>;
using sys_seconds = sys_time<std::chrono::seconds>;

struct local_t {};

template <class Duration>
using local_time = std::chrono::time_point<local_t, Duration>;

using local_seconds = local_time<std::chrono::seconds>;
using local_days = local_time<days>;

// types

struct last_spec {
    explicit last_spec() = default;
};

class day;
class month;
class year;

class weekday;
class weekday_indexed;
class weekday_last;

class month_day;
class month_day_last;
class month_weekday;
class month_weekday_last;

class year_month;

class year_month_day;
class year_month_day_last;
class year_month_weekday;
class year_month_weekday_last;

// date composition operators

CONSTCD11 year_month operator/(const year &y, const month &m) NOEXCEPT;
CONSTCD11 year_month operator/(const year &y, int m) NOEXCEPT;

CONSTCD11 month_day operator/(const day &d, const month &m) NOEXCEPT;
CONSTCD11 month_day operator/(const day &d, int m) NOEXCEPT;
CONSTCD11 month_day operator/(const month &m, const day &d) NOEXCEPT;
CONSTCD11 month_day operator/(const month &m, int d) NOEXCEPT;
CONSTCD11 month_day operator/(int m, const day &d) NOEXCEPT;

CONSTCD11 month_day_last operator/(const month &m, last_spec) NOEXCEPT;
CONSTCD11 month_day_last operator/(int m, last_spec) NOEXCEPT;
CONSTCD11 month_day_last operator/(last_spec, const month &m) NOEXCEPT;
CONSTCD11 month_day_last operator/(last_spec, int m) NOEXCEPT;

CONSTCD11 month_weekday operator/(const month &m, const weekday_indexed &wdi) NOEXCEPT;
CONSTCD11 month_weekday operator/(int m, const weekday_indexed &wdi) NOEXCEPT;
CONSTCD11 month_weekday operator/(const weekday_indexed &wdi, const month &m) NOEXCEPT;
CONSTCD11 month_weekday operator/(const weekday_indexed &wdi, int m) NOEXCEPT;

CONSTCD11 month_weekday_last operator/(const month &m, const weekday_last &wdl) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(int m, const weekday_last &wdl) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(const weekday_last &wdl, const month &m) NOEXCEPT;
CONSTCD11 month_weekday_last operator/(const weekday_last &wdl, int m) NOEXCEPT;

CONSTCD11 year_month_day operator/(const year_month &ym, const day &d) NOEXCEPT;
CONSTCD11 year_month_day operator/(const year_month &ym, int d) NOEXCEPT;
CONSTCD11 year_month_day operator/(const year &y, const month_day &md) NOEXCEPT;
CONSTCD11 year_month_day operator/(int y, const month_day &md) NOEXCEPT;
CONSTCD11 year_month_day operator/(const month_day &md, const year &y) NOEXCEPT;
CONSTCD11 year_month_day operator/(const month_day &md, int y) NOEXCEPT;

CONSTCD11
year_month_day_last operator/(const year_month &ym, last_spec) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const year &y, const month_day_last &mdl) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(int y, const month_day_last &mdl) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const month_day_last &mdl, const year &y) NOEXCEPT;
CONSTCD11
year_month_day_last operator/(const month_day_last &mdl, int y) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const year_month &ym, const weekday_indexed &wdi) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const year &y, const month_weekday &mwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(int y, const month_weekday &mwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const month_weekday &mwd, const year &y) NOEXCEPT;

CONSTCD11
year_month_weekday
operator/(const month_weekday &mwd, int y) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const year_month &ym, const weekday_last &wdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const year &y, const month_weekday_last &mwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(int y, const month_weekday_last &mwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const month_weekday_last &mwdl, const year &y) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator/(const month_weekday_last &mwdl, int y) NOEXCEPT;

// Detailed interface

// day

class day {
    unsigned char d_;

  public:
    day() = default;
    inline auto count() { return static_cast<unsigned>(d_); };
    explicit CONSTCD11 day(unsigned d) NOEXCEPT;

    CONSTCD14 day &operator++() NOEXCEPT;
    CONSTCD14 day operator++(int) NOEXCEPT;
    CONSTCD14 day &operator--() NOEXCEPT;
    CONSTCD14 day operator--(int) NOEXCEPT;

    CONSTCD14 day &operator+=(const days &d) NOEXCEPT;
    CONSTCD14 day &operator-=(const days &d) NOEXCEPT;

    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator<(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator>(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const day &x, const day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const day &x, const day &y) NOEXCEPT;

CONSTCD11 day operator+(const day &x, const days &y) NOEXCEPT;
CONSTCD11 day operator+(const days &x, const day &y) NOEXCEPT;
CONSTCD11 day operator-(const day &x, const days &y) NOEXCEPT;
CONSTCD11 days operator-(const day &x, const day &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const day &d);

// month

class month {
    unsigned char m_;

  public:
    month() = default;
    inline auto count() { return static_cast<unsigned>(m_); };
    explicit CONSTCD11 month(unsigned m) NOEXCEPT;

    CONSTCD14 month &operator++() NOEXCEPT;
    CONSTCD14 month operator++(int) NOEXCEPT;
    CONSTCD14 month &operator--() NOEXCEPT;
    CONSTCD14 month operator--(int) NOEXCEPT;

    CONSTCD14 month &operator+=(const months &m) NOEXCEPT;
    CONSTCD14 month &operator-=(const months &m) NOEXCEPT;

    CONSTCD11 explicit operator unsigned() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator<(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator>(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month &x, const month &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month &x, const month &y) NOEXCEPT;

CONSTCD14 month operator+(const month &x, const months &y) NOEXCEPT;
CONSTCD14 month operator+(const months &x, const month &y) NOEXCEPT;
CONSTCD14 month operator-(const month &x, const months &y) NOEXCEPT;
CONSTCD14 months operator-(const month &x, const month &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month &m);

// year

class year {
    short y_;

  public:
    year() = default;
    inline auto count() { return y_; };
    explicit CONSTCD11 year(int y) NOEXCEPT;

    CONSTCD14 year &operator++() NOEXCEPT;
    CONSTCD14 year operator++(int) NOEXCEPT;
    CONSTCD14 year &operator--() NOEXCEPT;
    CONSTCD14 year operator--(int) NOEXCEPT;

    CONSTCD14 year &operator+=(const years &y) NOEXCEPT;
    CONSTCD14 year &operator-=(const years &y) NOEXCEPT;

    CONSTCD11 year operator-() const NOEXCEPT;
    CONSTCD11 year operator+() const NOEXCEPT;

    CONSTCD11 bool is_leap() const NOEXCEPT;

    CONSTCD11 explicit operator int() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;

    static CONSTCD11 year min() NOEXCEPT;
    static CONSTCD11 year max() NOEXCEPT;
};

CONSTCD11 bool operator==(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator<(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator>(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year &x, const year &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year &x, const year &y) NOEXCEPT;

CONSTCD11 year operator+(const year &x, const years &y) NOEXCEPT;
CONSTCD11 year operator+(const years &x, const year &y) NOEXCEPT;
CONSTCD11 year operator-(const year &x, const years &y) NOEXCEPT;
CONSTCD11 years operator-(const year &x, const year &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year &y);

// weekday

class weekday {
    unsigned char wd_;

  public:
    weekday() = default;
    explicit CONSTCD11 weekday(unsigned wd) NOEXCEPT;
    CONSTCD11 weekday(const sys_days &dp) NOEXCEPT;
    CONSTCD11 explicit weekday(const local_days &dp) NOEXCEPT;

    CONSTCD14 weekday &operator++() NOEXCEPT;
    CONSTCD14 weekday operator++(int) NOEXCEPT;
    CONSTCD14 weekday &operator--() NOEXCEPT;
    CONSTCD14 weekday operator--(int) NOEXCEPT;

    CONSTCD14 weekday &operator+=(const days &d) NOEXCEPT;
    CONSTCD14 weekday &operator-=(const days &d) NOEXCEPT;

    CONSTCD11 bool ok() const NOEXCEPT;

    CONSTCD11 weekday_indexed operator[](unsigned index) const NOEXCEPT;
    CONSTCD11 weekday_last operator[](last_spec) const NOEXCEPT;

  private:
    static CONSTCD11 unsigned char weekday_from_days(int z) NOEXCEPT;

    friend CONSTCD11 bool operator==(const weekday &x, const weekday &y) NOEXCEPT;
    friend CONSTCD14 days operator-(const weekday &x, const weekday &y) NOEXCEPT;
    friend CONSTCD14 weekday operator+(const weekday &x, const days &y) NOEXCEPT;
    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd);
    friend class weekday_indexed;
};

CONSTCD11 bool operator==(const weekday &x, const weekday &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday &x, const weekday &y) NOEXCEPT;

CONSTCD14 weekday operator+(const weekday &x, const days &y) NOEXCEPT;
CONSTCD14 weekday operator+(const days &x, const weekday &y) NOEXCEPT;
CONSTCD14 weekday operator-(const weekday &x, const days &y) NOEXCEPT;
CONSTCD14 days operator-(const weekday &x, const weekday &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd);

// weekday_indexed

class weekday_indexed {
    unsigned char wd_ : 4;
    unsigned char index_ : 4;

  public:
    weekday_indexed() = default;
    CONSTCD11 weekday_indexed(const date::weekday &wd, unsigned index) NOEXCEPT;

    CONSTCD11 date::weekday weekday() const NOEXCEPT;
    CONSTCD11 unsigned index() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_indexed &wdi);

// weekday_last

class weekday_last {
    date::weekday wd_;

  public:
    explicit CONSTCD11 weekday_last(const date::weekday &wd) NOEXCEPT;

    CONSTCD11 date::weekday weekday() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const weekday_last &x, const weekday_last &y) NOEXCEPT;
CONSTCD11 bool operator!=(const weekday_last &x, const weekday_last &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_last &wdl);

namespace detail {

struct unspecified_month_disambiguator {};

} // namespace detail

// year_month

class year_month {
    date::year y_;
    date::month m_;

  public:
    year_month() = default;
    CONSTCD11 year_month(const date::year &y, const date::month &m) NOEXCEPT;

    CONSTCD11 date::year year() const NOEXCEPT;
    CONSTCD11 date::month month() const NOEXCEPT;

    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month &operator+=(const months &dm) NOEXCEPT;
    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month &operator-=(const months &dm) NOEXCEPT;
    CONSTCD14 year_month &operator+=(const years &dy) NOEXCEPT;
    CONSTCD14 year_month &operator-=(const years &dy) NOEXCEPT;

    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator<(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator>(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year_month &x, const year_month &y) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator+(const year_month &ym, const months &dm) NOEXCEPT;
template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator+(const months &dm, const year_month &ym) NOEXCEPT;
template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month operator-(const year_month &ym, const months &dm) NOEXCEPT;

CONSTCD11 months operator-(const year_month &x, const year_month &y) NOEXCEPT;
CONSTCD11 year_month operator+(const year_month &ym, const years &dy) NOEXCEPT;
CONSTCD11 year_month operator+(const years &dy, const year_month &ym) NOEXCEPT;
CONSTCD11 year_month operator-(const year_month &ym, const years &dy) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month &ym);

// month_day

class month_day {
    date::month m_;
    date::day d_;

  public:
    month_day() = default;
    CONSTCD11 month_day(const date::month &m, const date::day &d) NOEXCEPT;

    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::day day() const NOEXCEPT;

    CONSTCD14 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator<(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator>(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month_day &x, const month_day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month_day &x, const month_day &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day &md);

// month_day_last

class month_day_last {
    date::month m_;

  public:
    CONSTCD11 explicit month_day_last(const date::month &m) NOEXCEPT;

    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_day_last &x, const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_day_last &x, const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator<(const month_day_last &x, const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator>(const month_day_last &x, const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator<=(const month_day_last &x, const month_day_last &y) NOEXCEPT;
CONSTCD11 bool operator>=(const month_day_last &x, const month_day_last &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day_last &mdl);

// month_weekday

class month_weekday {
    date::month m_;
    date::weekday_indexed wdi_;

  public:
    CONSTCD11 month_weekday(const date::month &m,
                            const date::weekday_indexed &wdi) NOEXCEPT;

    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;

    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11 bool operator==(const month_weekday &x, const month_weekday &y) NOEXCEPT;
CONSTCD11 bool operator!=(const month_weekday &x, const month_weekday &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday &mwd);

// month_weekday_last

class month_weekday_last {
    date::month m_;
    date::weekday_last wdl_;

  public:
    CONSTCD11 month_weekday_last(const date::month &m,
                                 const date::weekday_last &wd) NOEXCEPT;

    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;

    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11
bool operator==(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT;
CONSTCD11
bool operator!=(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday_last &mwdl);

// class year_month_day

class year_month_day {
    date::year y_;
    date::month m_;
    date::day d_;

  public:
    year_month_day() = default;
    CONSTCD11 year_month_day(const date::year &y, const date::month &m,
                             const date::day &d) NOEXCEPT;
    CONSTCD14 year_month_day(const year_month_day_last &ymdl) NOEXCEPT;

    CONSTCD14 year_month_day(sys_days dp) NOEXCEPT;
    CONSTCD14 explicit year_month_day(local_days dp) NOEXCEPT;

    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_day &operator+=(const months &m) NOEXCEPT;
    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_day &operator-=(const months &m) NOEXCEPT;
    CONSTCD14 year_month_day &operator+=(const years &y) NOEXCEPT;
    CONSTCD14 year_month_day &operator-=(const years &y) NOEXCEPT;

    CONSTCD11 date::year year() const NOEXCEPT;
    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::day day() const NOEXCEPT;

    CONSTCD14 operator sys_days() const NOEXCEPT;
    CONSTCD14 explicit operator local_days() const NOEXCEPT;
    CONSTCD14 bool ok() const NOEXCEPT;

  private:
    static CONSTCD14 year_month_day from_days(days dp) NOEXCEPT;
    CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11 bool operator==(const year_month_day &x, const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator!=(const year_month_day &x, const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator<(const year_month_day &x, const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator>(const year_month_day &x, const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator<=(const year_month_day &x, const year_month_day &y) NOEXCEPT;
CONSTCD11 bool operator>=(const year_month_day &x, const year_month_day &y) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator+(const year_month_day &ymd, const months &dm) NOEXCEPT;
template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator+(const months &dm, const year_month_day &ymd) NOEXCEPT;
template <class = detail::unspecified_month_disambiguator>
CONSTCD14 year_month_day operator-(const year_month_day &ymd, const months &dm) NOEXCEPT;
CONSTCD11 year_month_day operator+(const year_month_day &ymd, const years &dy) NOEXCEPT;
CONSTCD11 year_month_day operator+(const years &dy, const year_month_day &ymd) NOEXCEPT;
CONSTCD11 year_month_day operator-(const year_month_day &ymd, const years &dy) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day &ymd);

// year_month_day_last

class year_month_day_last {
    date::year y_;
    date::month_day_last mdl_;

  public:
    CONSTCD11 year_month_day_last(const date::year &y,
                                  const date::month_day_last &mdl) NOEXCEPT;

    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_day_last &operator+=(const months &m) NOEXCEPT;
    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_day_last &operator-=(const months &m) NOEXCEPT;
    CONSTCD14 year_month_day_last &operator+=(const years &y) NOEXCEPT;
    CONSTCD14 year_month_day_last &operator-=(const years &y) NOEXCEPT;

    CONSTCD11 date::year year() const NOEXCEPT;
    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::month_day_last month_day_last() const NOEXCEPT;
    CONSTCD14 date::day day() const NOEXCEPT;

    CONSTCD14 operator sys_days() const NOEXCEPT;
    CONSTCD14 explicit operator local_days() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;
};

CONSTCD11
bool operator==(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator!=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator<(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator>(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator<=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;
CONSTCD11
bool operator>=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_day_last
    operator+(const year_month_day_last &ymdl, const months &dm) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_day_last
    operator+(const months &dm, const year_month_day_last &ymdl) NOEXCEPT;

CONSTCD11
year_month_day_last
operator+(const year_month_day_last &ymdl, const years &dy) NOEXCEPT;

CONSTCD11
year_month_day_last
operator+(const years &dy, const year_month_day_last &ymdl) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_day_last
    operator-(const year_month_day_last &ymdl, const months &dm) NOEXCEPT;

CONSTCD11
year_month_day_last
operator-(const year_month_day_last &ymdl, const years &dy) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day_last &ymdl);

// year_month_weekday

class year_month_weekday {
    date::year y_;
    date::month m_;
    date::weekday_indexed wdi_;

  public:
    year_month_weekday() = default;
    CONSTCD11 year_month_weekday(const date::year &y, const date::month &m,
                                 const date::weekday_indexed &wdi) NOEXCEPT;
    CONSTCD14 year_month_weekday(const sys_days &dp) NOEXCEPT;
    CONSTCD14 explicit year_month_weekday(const local_days &dp) NOEXCEPT;

    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_weekday &operator+=(const months &m) NOEXCEPT;
    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_weekday &operator-=(const months &m) NOEXCEPT;
    CONSTCD14 year_month_weekday &operator+=(const years &y) NOEXCEPT;
    CONSTCD14 year_month_weekday &operator-=(const years &y) NOEXCEPT;

    CONSTCD11 date::year year() const NOEXCEPT;
    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::weekday weekday() const NOEXCEPT;
    CONSTCD11 unsigned index() const NOEXCEPT;
    CONSTCD11 date::weekday_indexed weekday_indexed() const NOEXCEPT;

    CONSTCD14 operator sys_days() const NOEXCEPT;
    CONSTCD14 explicit operator local_days() const NOEXCEPT;
    CONSTCD14 bool ok() const NOEXCEPT;

  private:
    static CONSTCD14 year_month_weekday from_days(days dp) NOEXCEPT;
    CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11
bool operator==(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT;
CONSTCD11
bool operator!=(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday
    operator+(const year_month_weekday &ymwd, const months &dm) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday
    operator+(const months &dm, const year_month_weekday &ymwd) NOEXCEPT;

CONSTCD11
year_month_weekday
operator+(const year_month_weekday &ymwd, const years &dy) NOEXCEPT;

CONSTCD11
year_month_weekday
operator+(const years &dy, const year_month_weekday &ymwd) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday
    operator-(const year_month_weekday &ymwd, const months &dm) NOEXCEPT;

CONSTCD11
year_month_weekday
operator-(const year_month_weekday &ymwd, const years &dy) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_weekday &ymwdi);

// year_month_weekday_last

class year_month_weekday_last {
    date::year y_;
    date::month m_;
    date::weekday_last wdl_;

  public:
    CONSTCD11 year_month_weekday_last(const date::year &y, const date::month &m,
                                      const date::weekday_last &wdl) NOEXCEPT;

    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_weekday_last &operator+=(const months &m) NOEXCEPT;
    template <class = detail::unspecified_month_disambiguator>
    CONSTCD14 year_month_weekday_last &operator-=(const months &m) NOEXCEPT;
    CONSTCD14 year_month_weekday_last &operator+=(const years &y) NOEXCEPT;
    CONSTCD14 year_month_weekday_last &operator-=(const years &y) NOEXCEPT;

    CONSTCD11 date::year year() const NOEXCEPT;
    CONSTCD11 date::month month() const NOEXCEPT;
    CONSTCD11 date::weekday weekday() const NOEXCEPT;
    CONSTCD11 date::weekday_last weekday_last() const NOEXCEPT;

    CONSTCD14 operator sys_days() const NOEXCEPT;
    CONSTCD14 explicit operator local_days() const NOEXCEPT;
    CONSTCD11 bool ok() const NOEXCEPT;

  private:
    CONSTCD14 days to_days() const NOEXCEPT;
};

CONSTCD11
bool operator==(const year_month_weekday_last &x, const year_month_weekday_last &y) NOEXCEPT;

CONSTCD11
bool operator!=(const year_month_weekday_last &x, const year_month_weekday_last &y) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday_last
    operator+(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday_last
    operator+(const months &dm, const year_month_weekday_last &ymwdl) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator+(const years &dy, const year_month_weekday_last &ymwdl) NOEXCEPT;

template <class = detail::unspecified_month_disambiguator>
CONSTCD14
    year_month_weekday_last
    operator-(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT;

CONSTCD11
year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT;

template <class CharT, class Traits>
std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_weekday_last &ymwdl);

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
inline namespace literals {

CONSTCD11 date::day operator"" _d(unsigned long long d) NOEXCEPT;
CONSTCD11 date::year operator"" _y(unsigned long long y) NOEXCEPT;

} // namespace literals
#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)

// CONSTDATA date::month January{1};
// CONSTDATA date::month February{2};
// CONSTDATA date::month March{3};
// CONSTDATA date::month April{4};
// CONSTDATA date::month May{5};
// CONSTDATA date::month June{6};
// CONSTDATA date::month July{7};
// CONSTDATA date::month August{8};
// CONSTDATA date::month September{9};
// CONSTDATA date::month October{10};
// CONSTDATA date::month November{11};
// CONSTDATA date::month December{12};
//
// CONSTDATA date::weekday Sunday{0u};
// CONSTDATA date::weekday Monday{1u};
// CONSTDATA date::weekday Tuesday{2u};
// CONSTDATA date::weekday Wednesday{3u};
// CONSTDATA date::weekday Thursday{4u};
// CONSTDATA date::weekday Friday{5u};
// CONSTDATA date::weekday Saturday{6u};

#if HAS_VOID_T

template <class T, class = std::void_t<>>
struct is_clock
    : std::false_type {};

template <class T>
struct is_clock<T, std::void_t<decltype(T::now()), typename T::rep, typename T::period,
                               typename T::duration, typename T::time_point,
                               decltype(T::is_steady)>>
    : std::true_type {};

#endif // HAS_VOID_T

//----------------+
// Implementation |
//----------------+

// utilities
namespace detail {

template <class CharT, class Traits = std::char_traits<CharT>>
class save_istream {
  protected:
    std::basic_ios<CharT, Traits> &is_;
    CharT fill_;
    std::ios::fmtflags flags_;
    std::streamsize width_;
    std::basic_ostream<CharT, Traits> *tie_;
    std::locale loc_;

  public:
    ~save_istream() {
        is_.fill(fill_);
        is_.flags(flags_);
        is_.width(width_);
        is_.imbue(loc_);
        is_.tie(tie_);
    }

    save_istream(const save_istream &) = delete;
    save_istream &operator=(const save_istream &) = delete;

    explicit save_istream(std::basic_ios<CharT, Traits> &is)
        : is_(is), fill_(is.fill()), flags_(is.flags()), width_(is.width(0)), tie_(is.tie(nullptr)), loc_(is.getloc()) {
        if (tie_ != nullptr)
            tie_->flush();
    }
};

template <class CharT, class Traits = std::char_traits<CharT>>
class save_ostream
    : private save_istream<CharT, Traits> {
  public:
    ~save_ostream() {
        if ((this->flags_ & std::ios::unitbuf) &&
#if __cplusplus >= 201703
            std::uncaught_exceptions() == 0 &&
#else
            !std::uncaught_exception() &&
#endif
            this->is_.good())
            this->is_.rdbuf()->pubsync();
    }

    save_ostream(const save_ostream &) = delete;
    save_ostream &operator=(const save_ostream &) = delete;

    explicit save_ostream(std::basic_ios<CharT, Traits> &os)
        : save_istream<CharT, Traits>(os) {
    }
};

template <class T>
struct choose_trunc_type {
    static const int digits = std::numeric_limits<T>::digits;
    using type = typename std::conditional <
                 digits < 32,
          std::int32_t,
          typename std::conditional<
              digits<64,
                     std::int64_t,
#ifdef __SIZEOF_INT128__
                     __int128
#else
                     std::int64_t
#endif
                     >::type>::type;
};

template <class T>
CONSTCD11 inline
    typename std::enable_if<
        !std::chrono::treat_as_floating_point<T>::value,
        T>::type
    trunc(T t) NOEXCEPT {
    return t;
}

template <class T>
CONSTCD14 inline
    typename std::enable_if<
        std::chrono::treat_as_floating_point<T>::value,
        T>::type
    trunc(T t) NOEXCEPT {
    using namespace std;
    using I = typename choose_trunc_type<T>::type;
    CONSTDATA auto digits = numeric_limits<T>::digits;
    static_assert(digits < numeric_limits<I>::digits, "");
    CONSTDATA auto max = I{1} << (digits - 1);
    CONSTDATA auto min = -max;
    const auto negative = t < T{0};
    if (min <= t && t <= max && t != 0 && t == t) {
        t = static_cast<T>(static_cast<I>(t));
        if (t == 0 && negative)
            t = -t;
    }
    return t;
}

template <std::intmax_t Xp, std::intmax_t Yp>
struct static_gcd {
    static const std::intmax_t value = static_gcd<Yp, Xp % Yp>::value;
};

template <std::intmax_t Xp>
struct static_gcd<Xp, 0> {
    static const std::intmax_t value = Xp;
};

template <>
struct static_gcd<0, 0> {
    static const std::intmax_t value = 1;
};

template <class R1, class R2>
struct no_overflow {
  private:
    static const std::intmax_t gcd_n1_n2 = static_gcd<R1::num, R2::num>::value;
    static const std::intmax_t gcd_d1_d2 = static_gcd<R1::den, R2::den>::value;
    static const std::intmax_t n1 = R1::num / gcd_n1_n2;
    static const std::intmax_t d1 = R1::den / gcd_d1_d2;
    static const std::intmax_t n2 = R2::num / gcd_n1_n2;
    static const std::intmax_t d2 = R2::den / gcd_d1_d2;
    static const std::intmax_t max = -((std::intmax_t(1) << (sizeof(std::intmax_t) * CHAR_BIT - 1)) + 1);

    template <std::intmax_t Xp, std::intmax_t Yp, bool overflow>
    struct mul // overflow == false
    {
        static const std::intmax_t value = Xp * Yp;
    };

    template <std::intmax_t Xp, std::intmax_t Yp>
    struct mul<Xp, Yp, true> {
        static const std::intmax_t value = 1;
    };

  public:
    static const bool value = (n1 <= max / d2) && (n2 <= max / d1);
    typedef std::ratio<mul<n1, d2, !value>::value,
                       mul<n2, d1, !value>::value>
        type;
};

} // namespace detail

// trunc towards zero
template <class To, class Rep, class Period>
CONSTCD11 inline
    typename std::enable_if<
        detail::no_overflow<Period, typename To::period>::value,
        To>::type
    trunc(const std::chrono::duration<Rep, Period> &d) {
    return To{detail::trunc(std::chrono::duration_cast<To>(d).count())};
}

template <class To, class Rep, class Period>
CONSTCD11 inline
    typename std::enable_if<
        !detail::no_overflow<Period, typename To::period>::value,
        To>::type
    trunc(const std::chrono::duration<Rep, Period> &d) {
    using namespace std::chrono;
    using rep = typename std::common_type<Rep, typename To::rep>::type;
    return To{detail::trunc(duration_cast<To>(duration_cast<duration<rep>>(d)).count())};
}

#ifndef HAS_CHRONO_ROUNDING
#if defined(_MSC_FULL_VER) && (_MSC_FULL_VER >= 190023918 || (_MSC_FULL_VER >= 190000000 && defined(__clang__)))
#define HAS_CHRONO_ROUNDING 1
#elif defined(__cpp_lib_chrono) && __cplusplus > 201402 && __cpp_lib_chrono >= 201510
#define HAS_CHRONO_ROUNDING 1
#elif defined(_LIBCPP_VERSION) && __cplusplus > 201402 && _LIBCPP_VERSION >= 3800
#define HAS_CHRONO_ROUNDING 1
#else
#define HAS_CHRONO_ROUNDING 0
#endif
#endif // HAS_CHRONO_ROUNDING

#if HAS_CHRONO_ROUNDING == 0

// round down
template <class To, class Rep, class Period>
CONSTCD14 inline
    typename std::enable_if<
        detail::no_overflow<Period, typename To::period>::value,
        To>::type
    floor(const std::chrono::duration<Rep, Period> &d) {
    auto t = trunc<To>(d);
    if (t > d)
        return t - To{1};
    return t;
}

template <class To, class Rep, class Period>
CONSTCD14 inline
    typename std::enable_if<
        !detail::no_overflow<Period, typename To::period>::value,
        To>::type
    floor(const std::chrono::duration<Rep, Period> &d) {
    using namespace std::chrono;
    using rep = typename std::common_type<Rep, typename To::rep>::type;
    return floor<To>(floor<duration<rep>>(d));
}

// round to nearest, to even on tie
template <class To, class Rep, class Period>
CONSTCD14 inline To
round(const std::chrono::duration<Rep, Period> &d) {
    auto t0 = floor<To>(d);
    auto t1 = t0 + To{1};
    if (t1 == To{0} && t0 < To{0})
        t1 = -t1;
    auto diff0 = d - t0;
    auto diff1 = t1 - d;
    if (diff0 == diff1) {
        if (t0 - trunc<To>(t0 / 2) * 2 == To{0})
            return t0;
        return t1;
    }
    if (diff0 < diff1)
        return t0;
    return t1;
}

// round up
template <class To, class Rep, class Period>
CONSTCD14 inline To
ceil(const std::chrono::duration<Rep, Period> &d) {
    auto t = trunc<To>(d);
    if (t < d)
        return t + To{1};
    return t;
}

template <class Rep, class Period,
          class = typename std::enable_if<
              std::numeric_limits<Rep>::is_signed>::type>
CONSTCD11
    std::chrono::duration<Rep, Period>
    abs(std::chrono::duration<Rep, Period> d) {
    return d >= d.zero() ? d : -d;
}

// round down
template <class To, class Clock, class FromDuration>
CONSTCD11 inline std::chrono::time_point<Clock, To>
floor(const std::chrono::time_point<Clock, FromDuration> &tp) {
    using std::chrono::time_point;
    return time_point<Clock, To>{date::floor<To>(tp.time_since_epoch())};
}

// round to nearest, to even on tie
template <class To, class Clock, class FromDuration>
CONSTCD11 inline std::chrono::time_point<Clock, To>
round(const std::chrono::time_point<Clock, FromDuration> &tp) {
    using std::chrono::time_point;
    return time_point<Clock, To>{round<To>(tp.time_since_epoch())};
}

// round up
template <class To, class Clock, class FromDuration>
CONSTCD11 inline std::chrono::time_point<Clock, To>
ceil(const std::chrono::time_point<Clock, FromDuration> &tp) {
    using std::chrono::time_point;
    return time_point<Clock, To>{ceil<To>(tp.time_since_epoch())};
}

#else // HAS_CHRONO_ROUNDING == 1

using std::chrono::abs;
using std::chrono::ceil;
using std::chrono::floor;
using std::chrono::round;

#endif // HAS_CHRONO_ROUNDING

// trunc towards zero
template <class To, class Clock, class FromDuration>
CONSTCD11 inline std::chrono::time_point<Clock, To>
trunc(const std::chrono::time_point<Clock, FromDuration> &tp) {
    using std::chrono::time_point;
    return time_point<Clock, To>{trunc<To>(tp.time_since_epoch())};
}

// day

CONSTCD11 inline day::day(unsigned d) NOEXCEPT : d_(static_cast<unsigned char>(d)) {}
CONSTCD14 inline day &day::operator++() NOEXCEPT {
    ++d_;
    return *this;
}
CONSTCD14 inline day day::operator++(int) NOEXCEPT {
    auto tmp(*this);
    ++(*this);
    return tmp;
}
CONSTCD14 inline day &day::operator--() NOEXCEPT {
    --d_;
    return *this;
}
CONSTCD14 inline day day::operator--(int) NOEXCEPT {
    auto tmp(*this);
    --(*this);
    return tmp;
}
CONSTCD14 inline day &day::operator+=(const days &d) NOEXCEPT {
    *this = *this + d;
    return *this;
}
CONSTCD14 inline day &day::operator-=(const days &d) NOEXCEPT {
    *this = *this - d;
    return *this;
}
CONSTCD11 inline day::operator unsigned() const NOEXCEPT { return d_; }
CONSTCD11 inline bool day::ok() const NOEXCEPT { return 1 <= d_ && d_ <= 31; }

CONSTCD11
inline bool
operator==(const day &x, const day &y) NOEXCEPT {
    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
}

CONSTCD11
inline bool
operator!=(const day &x, const day &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const day &x, const day &y) NOEXCEPT {
    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
}

CONSTCD11
inline bool
operator>(const day &x, const day &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const day &x, const day &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const day &x, const day &y) NOEXCEPT {
    return !(x < y);
}

CONSTCD11
inline days
operator-(const day &x, const day &y) NOEXCEPT {
    return days{static_cast<days::rep>(static_cast<unsigned>(x) - static_cast<unsigned>(y))};
}

CONSTCD11
inline day
operator+(const day &x, const days &y) NOEXCEPT {
    return day{static_cast<unsigned>(x) + static_cast<unsigned>(y.count())};
}

CONSTCD11
inline day
operator+(const days &x, const day &y) NOEXCEPT {
    return y + x;
}

CONSTCD11
inline day
operator-(const day &x, const days &y) NOEXCEPT {
    return x + -y;
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const day &d) {
    detail::save_ostream<CharT, Traits> _(os);
    os.fill('0');
    os.flags(std::ios::dec | std::ios::right);
    os.width(2);
    os << static_cast<unsigned>(d);
    if (!d.ok())
        os << " is not a valid day";
    return os;
}

// month

CONSTCD11 inline month::month(unsigned m) NOEXCEPT : m_(static_cast<decltype(m_)>(m)) {}
CONSTCD14 inline month &month::operator++() NOEXCEPT {
    *this += months{1};
    return *this;
}
CONSTCD14 inline month month::operator++(int) NOEXCEPT {
    auto tmp(*this);
    ++(*this);
    return tmp;
}
CONSTCD14 inline month &month::operator--() NOEXCEPT {
    *this -= months{1};
    return *this;
}
CONSTCD14 inline month month::operator--(int) NOEXCEPT {
    auto tmp(*this);
    --(*this);
    return tmp;
}

CONSTCD14
inline month &
month::operator+=(const months &m) NOEXCEPT {
    *this = *this + m;
    return *this;
}

CONSTCD14
inline month &
month::operator-=(const months &m) NOEXCEPT {
    *this = *this - m;
    return *this;
}

CONSTCD11 inline month::operator unsigned() const NOEXCEPT { return m_; }
CONSTCD11 inline bool month::ok() const NOEXCEPT { return 1 <= m_ && m_ <= 12; }

CONSTCD11
inline bool
operator==(const month &x, const month &y) NOEXCEPT {
    return static_cast<unsigned>(x) == static_cast<unsigned>(y);
}

CONSTCD11
inline bool
operator!=(const month &x, const month &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const month &x, const month &y) NOEXCEPT {
    return static_cast<unsigned>(x) < static_cast<unsigned>(y);
}

CONSTCD11
inline bool
operator>(const month &x, const month &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const month &x, const month &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const month &x, const month &y) NOEXCEPT {
    return !(x < y);
}

CONSTCD14
inline months
operator-(const month &x, const month &y) NOEXCEPT {
    auto const d = static_cast<unsigned>(x) - static_cast<unsigned>(y);
    return months(d <= 11 ? d : d + 12);
}

CONSTCD14
inline month
operator+(const month &x, const months &y) NOEXCEPT {
    auto const mu = static_cast<long long>(static_cast<unsigned>(x)) + (y.count() - 1);
    auto const yr = (mu >= 0 ? mu : mu - 11) / 12;
    return month{static_cast<unsigned>(mu - yr * 12 + 1)};
}

CONSTCD14
inline month
operator+(const months &x, const month &y) NOEXCEPT {
    return y + x;
}

CONSTCD14
inline month
operator-(const month &x, const months &y) NOEXCEPT {
    return x + -y;
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month &m) {
    if (m.ok()) {
        CharT fmt[] = {'%', 'b', 0};
        os << format(os.getloc(), fmt, m);
    } else
        os << static_cast<unsigned>(m) << " is not a valid month";
    return os;
}

// year

CONSTCD11 inline year::year(int y) NOEXCEPT : y_(static_cast<decltype(y_)>(y)) {}
CONSTCD14 inline year &year::operator++() NOEXCEPT {
    ++y_;
    return *this;
}
CONSTCD14 inline year year::operator++(int) NOEXCEPT {
    auto tmp(*this);
    ++(*this);
    return tmp;
}
CONSTCD14 inline year &year::operator--() NOEXCEPT {
    --y_;
    return *this;
}
CONSTCD14 inline year year::operator--(int) NOEXCEPT {
    auto tmp(*this);
    --(*this);
    return tmp;
}
CONSTCD14 inline year &year::operator+=(const years &y) NOEXCEPT {
    *this = *this + y;
    return *this;
}
CONSTCD14 inline year &year::operator-=(const years &y) NOEXCEPT {
    *this = *this - y;
    return *this;
}
CONSTCD11 inline year year::operator-() const NOEXCEPT { return year{-y_}; }
CONSTCD11 inline year year::operator+() const NOEXCEPT { return *this; }

CONSTCD11
inline bool
year::is_leap() const NOEXCEPT {
    return y_ % 4 == 0 && (y_ % 100 != 0 || y_ % 400 == 0);
}

CONSTCD11 inline year::operator int() const NOEXCEPT { return y_; }

CONSTCD11
inline bool
year::ok() const NOEXCEPT {
    return y_ != std::numeric_limits<short>::min();
}

CONSTCD11
inline year
year::min() NOEXCEPT {
    return year{-32767};
}

CONSTCD11
inline year
year::max() NOEXCEPT {
    return year{32767};
}

CONSTCD11
inline bool
operator==(const year &x, const year &y) NOEXCEPT {
    return static_cast<int>(x) == static_cast<int>(y);
}

CONSTCD11
inline bool
operator!=(const year &x, const year &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const year &x, const year &y) NOEXCEPT {
    return static_cast<int>(x) < static_cast<int>(y);
}

CONSTCD11
inline bool
operator>(const year &x, const year &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const year &x, const year &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const year &x, const year &y) NOEXCEPT {
    return !(x < y);
}

CONSTCD11
inline years
operator-(const year &x, const year &y) NOEXCEPT {
    return years{static_cast<int>(x) - static_cast<int>(y)};
}

CONSTCD11
inline year
operator+(const year &x, const years &y) NOEXCEPT {
    return year{static_cast<int>(x) + y.count()};
}

CONSTCD11
inline year
operator+(const years &x, const year &y) NOEXCEPT {
    return y + x;
}

CONSTCD11
inline year
operator-(const year &x, const years &y) NOEXCEPT {
    return year{static_cast<int>(x) - y.count()};
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year &y) {
    detail::save_ostream<CharT, Traits> _(os);
    os.fill('0');
    os.flags(std::ios::dec | std::ios::internal);
    os.width(4 + (y < year{0}));
    os << static_cast<int>(y);
    if (!y.ok())
        os << " is not a valid year";
    return os;
}

// weekday

CONSTCD11
inline unsigned char
weekday::weekday_from_days(int z) NOEXCEPT {
    return static_cast<unsigned char>(static_cast<unsigned>(
        z >= -4 ? (z + 4) % 7 : (z + 5) % 7 + 6));
}

CONSTCD11
inline weekday::weekday(unsigned wd) NOEXCEPT
    : wd_(static_cast<decltype(wd_)>(wd != 7 ? wd : 0)) {}

CONSTCD11
inline weekday::weekday(const sys_days &dp) NOEXCEPT
    : wd_(weekday_from_days(dp.time_since_epoch().count())) {}

CONSTCD11
inline weekday::weekday(const local_days &dp) NOEXCEPT
    : wd_(weekday_from_days(dp.time_since_epoch().count())) {}

CONSTCD14 inline weekday &weekday::operator++() NOEXCEPT {
    *this += days{1};
    return *this;
}
CONSTCD14 inline weekday weekday::operator++(int) NOEXCEPT {
    auto tmp(*this);
    ++(*this);
    return tmp;
}
CONSTCD14 inline weekday &weekday::operator--() NOEXCEPT {
    *this -= days{1};
    return *this;
}
CONSTCD14 inline weekday weekday::operator--(int) NOEXCEPT {
    auto tmp(*this);
    --(*this);
    return tmp;
}

CONSTCD14
inline weekday &
weekday::operator+=(const days &d) NOEXCEPT {
    *this = *this + d;
    return *this;
}

CONSTCD14
inline weekday &
weekday::operator-=(const days &d) NOEXCEPT {
    *this = *this - d;
    return *this;
}

CONSTCD11 inline bool weekday::ok() const NOEXCEPT { return wd_ <= 6; }

CONSTCD11
inline bool
operator==(const weekday &x, const weekday &y) NOEXCEPT {
    return x.wd_ == y.wd_;
}

CONSTCD11
inline bool
operator!=(const weekday &x, const weekday &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD14
inline days
operator-(const weekday &x, const weekday &y) NOEXCEPT {
    auto const wdu = x.wd_ - y.wd_;
    auto const wk = (wdu >= 0 ? wdu : wdu - 6) / 7;
    return days{wdu - wk * 7};
}

CONSTCD14
inline weekday
operator+(const weekday &x, const days &y) NOEXCEPT {
    auto const wdu = static_cast<long long>(static_cast<unsigned>(x.wd_)) + y.count();
    auto const wk = (wdu >= 0 ? wdu : wdu - 6) / 7;
    return weekday{static_cast<unsigned>(wdu - wk * 7)};
}

CONSTCD14
inline weekday
operator+(const days &x, const weekday &y) NOEXCEPT {
    return y + x;
}

CONSTCD14
inline weekday
operator-(const weekday &x, const days &y) NOEXCEPT {
    return x + -y;
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday &wd) {
    if (wd.ok()) {
        CharT fmt[] = {'%', 'a', 0};
        os << format(fmt, wd);
    } else
        os << static_cast<unsigned>(wd.wd_) << " is not a valid weekday";
    return os;
}

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
inline namespace literals {

CONSTCD11
inline date::day
operator"" _d(unsigned long long d) NOEXCEPT {
    return date::day{static_cast<unsigned>(d)};
}

CONSTCD11
inline date::year
operator"" _y(unsigned long long y) NOEXCEPT {
    return date::year(static_cast<int>(y));
}
#endif // !defined(_MSC_VER) || (_MSC_VER >= 1900)

CONSTDATA date::last_spec last{};

CONSTDATA date::month jan{1};
CONSTDATA date::month feb{2};
CONSTDATA date::month mar{3};
CONSTDATA date::month apr{4};
CONSTDATA date::month may{5};
CONSTDATA date::month jun{6};
CONSTDATA date::month jul{7};
CONSTDATA date::month aug{8};
CONSTDATA date::month sep{9};
CONSTDATA date::month oct{10};
CONSTDATA date::month nov{11};
CONSTDATA date::month dec{12};

CONSTDATA date::weekday sun{0u};
CONSTDATA date::weekday mon{1u};
CONSTDATA date::weekday tue{2u};
CONSTDATA date::weekday wed{3u};
CONSTDATA date::weekday thu{4u};
CONSTDATA date::weekday fri{5u};
CONSTDATA date::weekday sat{6u};

#if !defined(_MSC_VER) || (_MSC_VER >= 1900)
} // inline namespace literals
#endif

CONSTDATA date::month January{1};
CONSTDATA date::month February{2};
CONSTDATA date::month March{3};
CONSTDATA date::month April{4};
CONSTDATA date::month May{5};
CONSTDATA date::month June{6};
CONSTDATA date::month July{7};
CONSTDATA date::month August{8};
CONSTDATA date::month September{9};
CONSTDATA date::month October{10};
CONSTDATA date::month November{11};
CONSTDATA date::month December{12};

CONSTDATA date::weekday Monday{1};
CONSTDATA date::weekday Tuesday{2};
CONSTDATA date::weekday Wednesday{3};
CONSTDATA date::weekday Thursday{4};
CONSTDATA date::weekday Friday{5};
CONSTDATA date::weekday Saturday{6};
CONSTDATA date::weekday Sunday{7};

// weekday_indexed

CONSTCD11
inline weekday
weekday_indexed::weekday() const NOEXCEPT {
    return date::weekday{static_cast<unsigned>(wd_)};
}

CONSTCD11 inline unsigned weekday_indexed::index() const NOEXCEPT { return index_; }

CONSTCD11
inline bool
weekday_indexed::ok() const NOEXCEPT {
    return weekday().ok() && 1 <= index_ && index_ <= 5;
}

#ifdef __GNUC__
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wconversion"
#endif // __GNUC__

CONSTCD11
inline weekday_indexed::weekday_indexed(const date::weekday &wd, unsigned index) NOEXCEPT
    : wd_(static_cast<decltype(wd_)>(static_cast<unsigned>(wd.wd_))),
      index_(static_cast<decltype(index_)>(index)) {}

#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif // __GNUC__

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_indexed &wdi) {
    os << wdi.weekday() << '[' << wdi.index();
    if (!(1 <= wdi.index() && wdi.index() <= 5))
        os << " is not a valid index";
    os << ']';
    return os;
}

CONSTCD11
inline weekday_indexed
    weekday::operator[](unsigned index) const NOEXCEPT {
    return {*this, index};
}

CONSTCD11
inline bool
operator==(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT {
    return x.weekday() == y.weekday() && x.index() == y.index();
}

CONSTCD11
inline bool
operator!=(const weekday_indexed &x, const weekday_indexed &y) NOEXCEPT {
    return !(x == y);
}

// weekday_last

CONSTCD11 inline date::weekday weekday_last::weekday() const NOEXCEPT { return wd_; }
CONSTCD11 inline bool weekday_last::ok() const NOEXCEPT { return wd_.ok(); }
CONSTCD11 inline weekday_last::weekday_last(const date::weekday &wd) NOEXCEPT : wd_(wd) {}

CONSTCD11
inline bool
operator==(const weekday_last &x, const weekday_last &y) NOEXCEPT {
    return x.weekday() == y.weekday();
}

CONSTCD11
inline bool
operator!=(const weekday_last &x, const weekday_last &y) NOEXCEPT {
    return !(x == y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const weekday_last &wdl) {
    return os << wdl.weekday() << "[last]";
}

CONSTCD11
inline weekday_last
    weekday::operator[](last_spec) const NOEXCEPT {
    return weekday_last{*this};
}

// year_month

CONSTCD11
inline year_month::year_month(const date::year &y, const date::month &m) NOEXCEPT
    : y_(y),
      m_(m) {}

CONSTCD11 inline year year_month::year() const NOEXCEPT { return y_; }
CONSTCD11 inline month year_month::month() const NOEXCEPT { return m_; }
CONSTCD11 inline bool year_month::ok() const NOEXCEPT { return y_.ok() && m_.ok(); }

template <class>
CONSTCD14 inline year_month &
year_month::operator+=(const months &dm) NOEXCEPT {
    *this = *this + dm;
    return *this;
}

template <class>
CONSTCD14 inline year_month &
year_month::operator-=(const months &dm) NOEXCEPT {
    *this = *this - dm;
    return *this;
}

CONSTCD14
inline year_month &
year_month::operator+=(const years &dy) NOEXCEPT {
    *this = *this + dy;
    return *this;
}

CONSTCD14
inline year_month &
year_month::operator-=(const years &dy) NOEXCEPT {
    *this = *this - dy;
    return *this;
}

CONSTCD11
inline bool
operator==(const year_month &x, const year_month &y) NOEXCEPT {
    return x.year() == y.year() && x.month() == y.month();
}

CONSTCD11
inline bool
operator!=(const year_month &x, const year_month &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const year_month &x, const year_month &y) NOEXCEPT {
    return x.year() < y.year() ? true
                               : (x.year() > y.year() ? false
                                                      : (x.month() < y.month()));
}

CONSTCD11
inline bool
operator>(const year_month &x, const year_month &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const year_month &x, const year_month &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const year_month &x, const year_month &y) NOEXCEPT {
    return !(x < y);
}

template <class>
CONSTCD14 inline year_month
operator+(const year_month &ym, const months &dm) NOEXCEPT {
    auto dmi = static_cast<int>(static_cast<unsigned>(ym.month())) - 1 + dm.count();
    auto dy = (dmi >= 0 ? dmi : dmi - 11) / 12;
    dmi = dmi - dy * 12 + 1;
    return (ym.year() + years(dy)) / month(static_cast<unsigned>(dmi));
}

template <class>
CONSTCD14 inline year_month
operator+(const months &dm, const year_month &ym) NOEXCEPT {
    return ym + dm;
}

template <class>
CONSTCD14 inline year_month
operator-(const year_month &ym, const months &dm) NOEXCEPT {
    return ym + -dm;
}

CONSTCD11
inline months
operator-(const year_month &x, const year_month &y) NOEXCEPT {
    return (x.year() - y.year()) +
           months(static_cast<unsigned>(x.month()) - static_cast<unsigned>(y.month()));
}

CONSTCD11
inline year_month
operator+(const year_month &ym, const years &dy) NOEXCEPT {
    return (ym.year() + dy) / ym.month();
}

CONSTCD11
inline year_month
operator+(const years &dy, const year_month &ym) NOEXCEPT {
    return ym + dy;
}

CONSTCD11
inline year_month
operator-(const year_month &ym, const years &dy) NOEXCEPT {
    return ym + -dy;
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month &ym) {
    return os << ym.year() << '/' << ym.month();
}

// month_day

CONSTCD11
inline month_day::month_day(const date::month &m, const date::day &d) NOEXCEPT
    : m_(m),
      d_(d) {}

CONSTCD11 inline date::month month_day::month() const NOEXCEPT { return m_; }
CONSTCD11 inline date::day month_day::day() const NOEXCEPT { return d_; }

CONSTCD14
inline bool
month_day::ok() const NOEXCEPT {
    CONSTDATA date::day d[] =
        {
            date::day(31), date::day(29), date::day(31),
            date::day(30), date::day(31), date::day(30),
            date::day(31), date::day(31), date::day(30),
            date::day(31), date::day(30), date::day(31)};
    return m_.ok() && date::day{1} <= d_ && d_ <= d[static_cast<unsigned>(m_) - 1];
}

CONSTCD11
inline bool
operator==(const month_day &x, const month_day &y) NOEXCEPT {
    return x.month() == y.month() && x.day() == y.day();
}

CONSTCD11
inline bool
operator!=(const month_day &x, const month_day &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const month_day &x, const month_day &y) NOEXCEPT {
    return x.month() < y.month() ? true
                                 : (x.month() > y.month() ? false
                                                          : (x.day() < y.day()));
}

CONSTCD11
inline bool
operator>(const month_day &x, const month_day &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const month_day &x, const month_day &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const month_day &x, const month_day &y) NOEXCEPT {
    return !(x < y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day &md) {
    return os << md.month() << '/' << md.day();
}

// month_day_last

CONSTCD11 inline month month_day_last::month() const NOEXCEPT { return m_; }
CONSTCD11 inline bool month_day_last::ok() const NOEXCEPT { return m_.ok(); }
CONSTCD11 inline month_day_last::month_day_last(const date::month &m) NOEXCEPT : m_(m) {}

CONSTCD11
inline bool
operator==(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return x.month() == y.month();
}

CONSTCD11
inline bool
operator!=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return x.month() < y.month();
}

CONSTCD11
inline bool
operator>(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const month_day_last &x, const month_day_last &y) NOEXCEPT {
    return !(x < y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_day_last &mdl) {
    return os << mdl.month() << "/last";
}

// month_weekday

CONSTCD11
inline month_weekday::month_weekday(const date::month &m,
                                    const date::weekday_indexed &wdi) NOEXCEPT
    : m_(m),
      wdi_(wdi) {}

CONSTCD11 inline month month_weekday::month() const NOEXCEPT { return m_; }

CONSTCD11
inline weekday_indexed
month_weekday::weekday_indexed() const NOEXCEPT {
    return wdi_;
}

CONSTCD11
inline bool
month_weekday::ok() const NOEXCEPT {
    return m_.ok() && wdi_.ok();
}

CONSTCD11
inline bool
operator==(const month_weekday &x, const month_weekday &y) NOEXCEPT {
    return x.month() == y.month() && x.weekday_indexed() == y.weekday_indexed();
}

CONSTCD11
inline bool
operator!=(const month_weekday &x, const month_weekday &y) NOEXCEPT {
    return !(x == y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday &mwd) {
    return os << mwd.month() << '/' << mwd.weekday_indexed();
}

// month_weekday_last

CONSTCD11
inline month_weekday_last::month_weekday_last(const date::month &m,
                                              const date::weekday_last &wdl) NOEXCEPT
    : m_(m),
      wdl_(wdl) {}

CONSTCD11 inline month month_weekday_last::month() const NOEXCEPT { return m_; }

CONSTCD11
inline weekday_last
month_weekday_last::weekday_last() const NOEXCEPT {
    return wdl_;
}

CONSTCD11
inline bool
month_weekday_last::ok() const NOEXCEPT {
    return m_.ok() && wdl_.ok();
}

CONSTCD11
inline bool
operator==(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT {
    return x.month() == y.month() && x.weekday_last() == y.weekday_last();
}

CONSTCD11
inline bool
operator!=(const month_weekday_last &x, const month_weekday_last &y) NOEXCEPT {
    return !(x == y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const month_weekday_last &mwdl) {
    return os << mwdl.month() << '/' << mwdl.weekday_last();
}

// year_month_day_last

CONSTCD11
inline year_month_day_last::year_month_day_last(const date::year &y,
                                                const date::month_day_last &mdl) NOEXCEPT
    : y_(y),
      mdl_(mdl) {}

template <class>
CONSTCD14 inline year_month_day_last &
year_month_day_last::operator+=(const months &m) NOEXCEPT {
    *this = *this + m;
    return *this;
}

template <class>
CONSTCD14 inline year_month_day_last &
year_month_day_last::operator-=(const months &m) NOEXCEPT {
    *this = *this - m;
    return *this;
}

CONSTCD14
inline year_month_day_last &
year_month_day_last::operator+=(const years &y) NOEXCEPT {
    *this = *this + y;
    return *this;
}

CONSTCD14
inline year_month_day_last &
year_month_day_last::operator-=(const years &y) NOEXCEPT {
    *this = *this - y;
    return *this;
}

CONSTCD11 inline year year_month_day_last::year() const NOEXCEPT { return y_; }
CONSTCD11 inline month year_month_day_last::month() const NOEXCEPT { return mdl_.month(); }

CONSTCD11
inline month_day_last
year_month_day_last::month_day_last() const NOEXCEPT {
    return mdl_;
}

CONSTCD14
inline day
year_month_day_last::day() const NOEXCEPT {
    CONSTDATA date::day d[] =
        {
            date::day(31), date::day(28), date::day(31),
            date::day(30), date::day(31), date::day(30),
            date::day(31), date::day(31), date::day(30),
            date::day(31), date::day(30), date::day(31)};
    return month() != February || !y_.is_leap() ? d[static_cast<unsigned>(month()) - 1] : date::day{29};
}

CONSTCD14
inline year_month_day_last::operator sys_days() const NOEXCEPT {
    return sys_days(year() / month() / day());
}

CONSTCD14
inline year_month_day_last::operator local_days() const NOEXCEPT {
    return local_days(year() / month() / day());
}

CONSTCD11
inline bool
year_month_day_last::ok() const NOEXCEPT {
    return y_.ok() && mdl_.ok();
}

CONSTCD11
inline bool
operator==(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return x.year() == y.year() && x.month_day_last() == y.month_day_last();
}

CONSTCD11
inline bool
operator!=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return x.year() < y.year() ? true
                               : (x.year() > y.year() ? false
                                                      : (x.month_day_last() < y.month_day_last()));
}

CONSTCD11
inline bool
operator>(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const year_month_day_last &x, const year_month_day_last &y) NOEXCEPT {
    return !(x < y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day_last &ymdl) {
    return os << ymdl.year() << '/' << ymdl.month_day_last();
}

template <class>
CONSTCD14 inline year_month_day_last
operator+(const year_month_day_last &ymdl, const months &dm) NOEXCEPT {
    return (ymdl.year() / ymdl.month() + dm) / last;
}

template <class>
CONSTCD14 inline year_month_day_last
operator+(const months &dm, const year_month_day_last &ymdl) NOEXCEPT {
    return ymdl + dm;
}

template <class>
CONSTCD14 inline year_month_day_last
operator-(const year_month_day_last &ymdl, const months &dm) NOEXCEPT {
    return ymdl + (-dm);
}

CONSTCD11
inline year_month_day_last
operator+(const year_month_day_last &ymdl, const years &dy) NOEXCEPT {
    return {ymdl.year() + dy, ymdl.month_day_last()};
}

CONSTCD11
inline year_month_day_last
operator+(const years &dy, const year_month_day_last &ymdl) NOEXCEPT {
    return ymdl + dy;
}

CONSTCD11
inline year_month_day_last
operator-(const year_month_day_last &ymdl, const years &dy) NOEXCEPT {
    return ymdl + (-dy);
}

// year_month_day

CONSTCD11
inline year_month_day::year_month_day(const date::year &y, const date::month &m,
                                      const date::day &d) NOEXCEPT
    : y_(y),
      m_(m),
      d_(d) {}

CONSTCD14
inline year_month_day::year_month_day(const year_month_day_last &ymdl) NOEXCEPT
    : y_(ymdl.year()),
      m_(ymdl.month()),
      d_(ymdl.day()) {}

CONSTCD14
inline year_month_day::year_month_day(sys_days dp) NOEXCEPT
    : year_month_day(from_days(dp.time_since_epoch())) {}

CONSTCD14
inline year_month_day::year_month_day(local_days dp) NOEXCEPT
    : year_month_day(from_days(dp.time_since_epoch())) {}

CONSTCD11 inline year year_month_day::year() const NOEXCEPT { return y_; }
CONSTCD11 inline month year_month_day::month() const NOEXCEPT { return m_; }
CONSTCD11 inline day year_month_day::day() const NOEXCEPT { return d_; }

template <class>
CONSTCD14 inline year_month_day &
year_month_day::operator+=(const months &m) NOEXCEPT {
    *this = *this + m;
    return *this;
}

template <class>
CONSTCD14 inline year_month_day &
year_month_day::operator-=(const months &m) NOEXCEPT {
    *this = *this - m;
    return *this;
}

CONSTCD14
inline year_month_day &
year_month_day::operator+=(const years &y) NOEXCEPT {
    *this = *this + y;
    return *this;
}

CONSTCD14
inline year_month_day &
year_month_day::operator-=(const years &y) NOEXCEPT {
    *this = *this - y;
    return *this;
}

CONSTCD14
inline days
year_month_day::to_days() const NOEXCEPT {
    static_assert(std::numeric_limits<unsigned>::digits >= 18,
                  "This algorithm has not been ported to a 16 bit unsigned integer");
    static_assert(std::numeric_limits<int>::digits >= 20,
                  "This algorithm has not been ported to a 16 bit signed integer");
    auto const y = static_cast<int>(y_) - (m_ <= February);
    auto const m = static_cast<unsigned>(m_);
    auto const d = static_cast<unsigned>(d_);
    auto const era = (y >= 0 ? y : y - 399) / 400;
    auto const yoe = static_cast<unsigned>(y - era * 400);            // [0, 399]
    auto const doy = (153 * (m > 2 ? m - 3 : m + 9) + 2) / 5 + d - 1; // [0, 365]
    auto const doe = yoe * 365 + yoe / 4 - yoe / 100 + doy;           // [0, 146096]
    return days{era * 146097 + static_cast<int>(doe) - 719468};
}

CONSTCD14
inline year_month_day::operator sys_days() const NOEXCEPT {
    return sys_days{to_days()};
}

CONSTCD14
inline year_month_day::operator local_days() const NOEXCEPT {
    return local_days{to_days()};
}

CONSTCD14
inline bool
year_month_day::ok() const NOEXCEPT {
    if (!(y_.ok() && m_.ok()))
        return false;
    return date::day{1} <= d_ && d_ <= (y_ / m_ / last).day();
}

CONSTCD11
inline bool
operator==(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return x.year() == y.year() && x.month() == y.month() && x.day() == y.day();
}

CONSTCD11
inline bool
operator!=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return !(x == y);
}

CONSTCD11
inline bool
operator<(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return x.year() < y.year() ? true
                               : (x.year() > y.year() ? false
                                                      : (x.month() < y.month() ? true
                                                                               : (x.month() > y.month() ? false
                                                                                                        : (x.day() < y.day()))));
}

CONSTCD11
inline bool
operator>(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return y < x;
}

CONSTCD11
inline bool
operator<=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return !(y < x);
}

CONSTCD11
inline bool
operator>=(const year_month_day &x, const year_month_day &y) NOEXCEPT {
    return !(x < y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_day &ymd) {
    detail::save_ostream<CharT, Traits> _(os);
    os.fill('0');
    os.flags(std::ios::dec | std::ios::right);
    os << ymd.year() << '-';
    os.width(2);
    os << static_cast<unsigned>(ymd.month()) << '-';
    os << ymd.day();
    if (!ymd.ok())
        os << " is not a valid date";
    return os;
}

CONSTCD14
inline year_month_day
year_month_day::from_days(days dp) NOEXCEPT {
    static_assert(std::numeric_limits<unsigned>::digits >= 18,
                  "This algorithm has not been ported to a 16 bit unsigned integer");
    static_assert(std::numeric_limits<int>::digits >= 20,
                  "This algorithm has not been ported to a 16 bit signed integer");
    auto const z = dp.count() + 719468;
    auto const era = (z >= 0 ? z : z - 146096) / 146097;
    auto const doe = static_cast<unsigned>(z - era * 146097);               // [0, 146096]
    auto const yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365; // [0, 399]
    auto const y = static_cast<days::rep>(yoe) + era * 400;
    auto const doy = doe - (365 * yoe + yoe / 4 - yoe / 100); // [0, 365]
    auto const mp = (5 * doy + 2) / 153;                      // [0, 11]
    auto const d = doy - (153 * mp + 2) / 5 + 1;              // [1, 31]
    auto const m = mp < 10 ? mp + 3 : mp - 9;                 // [1, 12]
    return year_month_day{date::year{y + (m <= 2)}, date::month(m), date::day(d)};
}

template <class>
CONSTCD14 inline year_month_day
operator+(const year_month_day &ymd, const months &dm) NOEXCEPT {
    return (ymd.year() / ymd.month() + dm) / ymd.day();
}

template <class>
CONSTCD14 inline year_month_day
operator+(const months &dm, const year_month_day &ymd) NOEXCEPT {
    return ymd + dm;
}

template <class>
CONSTCD14 inline year_month_day
operator-(const year_month_day &ymd, const months &dm) NOEXCEPT {
    return ymd + (-dm);
}

CONSTCD11
inline year_month_day
operator+(const year_month_day &ymd, const years &dy) NOEXCEPT {
    return (ymd.year() + dy) / ymd.month() / ymd.day();
}

CONSTCD11
inline year_month_day
operator+(const years &dy, const year_month_day &ymd) NOEXCEPT {
    return ymd + dy;
}

CONSTCD11
inline year_month_day
operator-(const year_month_day &ymd, const years &dy) NOEXCEPT {
    return ymd + (-dy);
}

// year_month_weekday

CONSTCD11
inline year_month_weekday::year_month_weekday(const date::year &y, const date::month &m,
                                              const date::weekday_indexed &wdi)
    NOEXCEPT
    : y_(y),
      m_(m),
      wdi_(wdi) {}

CONSTCD14
inline year_month_weekday::year_month_weekday(const sys_days &dp) NOEXCEPT
    : year_month_weekday(from_days(dp.time_since_epoch())) {}

CONSTCD14
inline year_month_weekday::year_month_weekday(const local_days &dp) NOEXCEPT
    : year_month_weekday(from_days(dp.time_since_epoch())) {}

template <class>
CONSTCD14 inline year_month_weekday &
year_month_weekday::operator+=(const months &m) NOEXCEPT {
    *this = *this + m;
    return *this;
}

template <class>
CONSTCD14 inline year_month_weekday &
year_month_weekday::operator-=(const months &m) NOEXCEPT {
    *this = *this - m;
    return *this;
}

CONSTCD14
inline year_month_weekday &
year_month_weekday::operator+=(const years &y) NOEXCEPT {
    *this = *this + y;
    return *this;
}

CONSTCD14
inline year_month_weekday &
year_month_weekday::operator-=(const years &y) NOEXCEPT {
    *this = *this - y;
    return *this;
}

CONSTCD11 inline year year_month_weekday::year() const NOEXCEPT { return y_; }
CONSTCD11 inline month year_month_weekday::month() const NOEXCEPT { return m_; }

CONSTCD11
inline weekday
year_month_weekday::weekday() const NOEXCEPT {
    return wdi_.weekday();
}

CONSTCD11
inline unsigned
year_month_weekday::index() const NOEXCEPT {
    return wdi_.index();
}

CONSTCD11
inline weekday_indexed
year_month_weekday::weekday_indexed() const NOEXCEPT {
    return wdi_;
}

CONSTCD14
inline year_month_weekday::operator sys_days() const NOEXCEPT {
    return sys_days{to_days()};
}

CONSTCD14
inline year_month_weekday::operator local_days() const NOEXCEPT {
    return local_days{to_days()};
}

CONSTCD14
inline bool
year_month_weekday::ok() const NOEXCEPT {
    if (!y_.ok() || !m_.ok() || !wdi_.weekday().ok() || wdi_.index() < 1)
        return false;
    if (wdi_.index() <= 4)
        return true;
    auto d2 = wdi_.weekday() - date::weekday(static_cast<sys_days>(y_ / m_ / 1)) +
              days((wdi_.index() - 1) * 7 + 1);
    return static_cast<unsigned>(d2.count()) <= static_cast<unsigned>((y_ / m_ / last).day());
}

CONSTCD14
inline year_month_weekday
year_month_weekday::from_days(days d) NOEXCEPT {
    sys_days dp{d};
    auto const wd = date::weekday(dp);
    auto const ymd = year_month_day(dp);
    return {ymd.year(), ymd.month(), wd[(static_cast<unsigned>(ymd.day()) - 1) / 7 + 1]};
}

CONSTCD14
inline days
year_month_weekday::to_days() const NOEXCEPT {
    auto d = sys_days(y_ / m_ / 1);
    return (d + (wdi_.weekday() - date::weekday(d) + days{(wdi_.index() - 1) * 7})).time_since_epoch();
}

CONSTCD11
inline bool
operator==(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT {
    return x.year() == y.year() && x.month() == y.month() &&
           x.weekday_indexed() == y.weekday_indexed();
}

CONSTCD11
inline bool
operator!=(const year_month_weekday &x, const year_month_weekday &y) NOEXCEPT {
    return !(x == y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_weekday &ymwdi) {
    return os << ymwdi.year() << '/' << ymwdi.month()
              << '/' << ymwdi.weekday_indexed();
}

template <class>
CONSTCD14 inline year_month_weekday
operator+(const year_month_weekday &ymwd, const months &dm) NOEXCEPT {
    return (ymwd.year() / ymwd.month() + dm) / ymwd.weekday_indexed();
}

template <class>
CONSTCD14 inline year_month_weekday
operator+(const months &dm, const year_month_weekday &ymwd) NOEXCEPT {
    return ymwd + dm;
}

template <class>
CONSTCD14 inline year_month_weekday
operator-(const year_month_weekday &ymwd, const months &dm) NOEXCEPT {
    return ymwd + (-dm);
}

CONSTCD11
inline year_month_weekday
operator+(const year_month_weekday &ymwd, const years &dy) NOEXCEPT {
    return {ymwd.year() + dy, ymwd.month(), ymwd.weekday_indexed()};
}

CONSTCD11
inline year_month_weekday
operator+(const years &dy, const year_month_weekday &ymwd) NOEXCEPT {
    return ymwd + dy;
}

CONSTCD11
inline year_month_weekday
operator-(const year_month_weekday &ymwd, const years &dy) NOEXCEPT {
    return ymwd + (-dy);
}

// year_month_weekday_last

CONSTCD11
inline year_month_weekday_last::year_month_weekday_last(const date::year &y,
                                                        const date::month &m,
                                                        const date::weekday_last &wdl) NOEXCEPT
    : y_(y),
      m_(m),
      wdl_(wdl) {}

template <class>
CONSTCD14 inline year_month_weekday_last &
year_month_weekday_last::operator+=(const months &m) NOEXCEPT {
    *this = *this + m;
    return *this;
}

template <class>
CONSTCD14 inline year_month_weekday_last &
year_month_weekday_last::operator-=(const months &m) NOEXCEPT {
    *this = *this - m;
    return *this;
}

CONSTCD14
inline year_month_weekday_last &
year_month_weekday_last::operator+=(const years &y) NOEXCEPT {
    *this = *this + y;
    return *this;
}

CONSTCD14
inline year_month_weekday_last &
year_month_weekday_last::operator-=(const years &y) NOEXCEPT {
    *this = *this - y;
    return *this;
}

CONSTCD11 inline year year_month_weekday_last::year() const NOEXCEPT { return y_; }
CONSTCD11 inline month year_month_weekday_last::month() const NOEXCEPT { return m_; }

CONSTCD11
inline weekday
year_month_weekday_last::weekday() const NOEXCEPT {
    return wdl_.weekday();
}

CONSTCD11
inline weekday_last
year_month_weekday_last::weekday_last() const NOEXCEPT {
    return wdl_;
}

CONSTCD14
inline year_month_weekday_last::operator sys_days() const NOEXCEPT {
    return sys_days{to_days()};
}

CONSTCD14
inline year_month_weekday_last::operator local_days() const NOEXCEPT {
    return local_days{to_days()};
}

CONSTCD11
inline bool
year_month_weekday_last::ok() const NOEXCEPT {
    return y_.ok() && m_.ok() && wdl_.ok();
}

CONSTCD14
inline days
year_month_weekday_last::to_days() const NOEXCEPT {
    auto const d = sys_days(y_ / m_ / last);
    return (d - (date::weekday{d} - wdl_.weekday())).time_since_epoch();
}

CONSTCD11
inline bool
operator==(const year_month_weekday_last &x, const year_month_weekday_last &y) NOEXCEPT {
    return x.year() == y.year() && x.month() == y.month() &&
           x.weekday_last() == y.weekday_last();
}

CONSTCD11
inline bool
operator!=(const year_month_weekday_last &x, const year_month_weekday_last &y) NOEXCEPT {
    return !(x == y);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const year_month_weekday_last &ymwdl) {
    return os << ymwdl.year() << '/' << ymwdl.month() << '/' << ymwdl.weekday_last();
}

template <class>
CONSTCD14 inline year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT {
    return (ymwdl.year() / ymwdl.month() + dm) / ymwdl.weekday_last();
}

template <class>
CONSTCD14 inline year_month_weekday_last
operator+(const months &dm, const year_month_weekday_last &ymwdl) NOEXCEPT {
    return ymwdl + dm;
}

template <class>
CONSTCD14 inline year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const months &dm) NOEXCEPT {
    return ymwdl + (-dm);
}

CONSTCD11
inline year_month_weekday_last
operator+(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT {
    return {ymwdl.year() + dy, ymwdl.month(), ymwdl.weekday_last()};
}

CONSTCD11
inline year_month_weekday_last
operator+(const years &dy, const year_month_weekday_last &ymwdl) NOEXCEPT {
    return ymwdl + dy;
}

CONSTCD11
inline year_month_weekday_last
operator-(const year_month_weekday_last &ymwdl, const years &dy) NOEXCEPT {
    return ymwdl + (-dy);
}

// year_month from operator/()

CONSTCD11
inline year_month
operator/(const year &y, const month &m) NOEXCEPT {
    return {y, m};
}

CONSTCD11
inline year_month
operator/(const year &y, int m) NOEXCEPT {
    return y / month(static_cast<unsigned>(m));
}

// month_day from operator/()

CONSTCD11
inline month_day
operator/(const month &m, const day &d) NOEXCEPT {
    return {m, d};
}

CONSTCD11
inline month_day
operator/(const day &d, const month &m) NOEXCEPT {
    return m / d;
}

CONSTCD11
inline month_day
operator/(const month &m, int d) NOEXCEPT {
    return m / day(static_cast<unsigned>(d));
}

CONSTCD11
inline month_day
operator/(int m, const day &d) NOEXCEPT {
    return month(static_cast<unsigned>(m)) / d;
}

CONSTCD11 inline month_day operator/(const day &d, int m) NOEXCEPT { return m / d; }

// month_day_last from operator/()

CONSTCD11
inline month_day_last
operator/(const month &m, last_spec) NOEXCEPT {
    return month_day_last{m};
}

CONSTCD11
inline month_day_last
operator/(last_spec, const month &m) NOEXCEPT {
    return m / last;
}

CONSTCD11
inline month_day_last
operator/(int m, last_spec) NOEXCEPT {
    return month(static_cast<unsigned>(m)) / last;
}

CONSTCD11
inline month_day_last
operator/(last_spec, int m) NOEXCEPT {
    return m / last;
}

// month_weekday from operator/()

CONSTCD11
inline month_weekday
operator/(const month &m, const weekday_indexed &wdi) NOEXCEPT {
    return {m, wdi};
}

CONSTCD11
inline month_weekday
operator/(const weekday_indexed &wdi, const month &m) NOEXCEPT {
    return m / wdi;
}

CONSTCD11
inline month_weekday
operator/(int m, const weekday_indexed &wdi) NOEXCEPT {
    return month(static_cast<unsigned>(m)) / wdi;
}

CONSTCD11
inline month_weekday
operator/(const weekday_indexed &wdi, int m) NOEXCEPT {
    return m / wdi;
}

// month_weekday_last from operator/()

CONSTCD11
inline month_weekday_last
operator/(const month &m, const weekday_last &wdl) NOEXCEPT {
    return {m, wdl};
}

CONSTCD11
inline month_weekday_last
operator/(const weekday_last &wdl, const month &m) NOEXCEPT {
    return m / wdl;
}

CONSTCD11
inline month_weekday_last
operator/(int m, const weekday_last &wdl) NOEXCEPT {
    return month(static_cast<unsigned>(m)) / wdl;
}

CONSTCD11
inline month_weekday_last
operator/(const weekday_last &wdl, int m) NOEXCEPT {
    return m / wdl;
}

// year_month_day from operator/()

CONSTCD11
inline year_month_day
operator/(const year_month &ym, const day &d) NOEXCEPT {
    return {ym.year(), ym.month(), d};
}

CONSTCD11
inline year_month_day
operator/(const year_month &ym, int d) NOEXCEPT {
    return ym / day(static_cast<unsigned>(d));
}

CONSTCD11
inline year_month_day
operator/(const year &y, const month_day &md) NOEXCEPT {
    return y / md.month() / md.day();
}

CONSTCD11
inline year_month_day
operator/(int y, const month_day &md) NOEXCEPT {
    return year(y) / md;
}

CONSTCD11
inline year_month_day
operator/(const month_day &md, const year &y) NOEXCEPT {
    return y / md;
}

CONSTCD11
inline year_month_day
operator/(const month_day &md, int y) NOEXCEPT {
    return year(y) / md;
}

// year_month_day_last from operator/()

CONSTCD11
inline year_month_day_last
operator/(const year_month &ym, last_spec) NOEXCEPT {
    return {ym.year(), month_day_last{ym.month()}};
}

CONSTCD11
inline year_month_day_last
operator/(const year &y, const month_day_last &mdl) NOEXCEPT {
    return {y, mdl};
}

CONSTCD11
inline year_month_day_last
operator/(int y, const month_day_last &mdl) NOEXCEPT {
    return year(y) / mdl;
}

CONSTCD11
inline year_month_day_last
operator/(const month_day_last &mdl, const year &y) NOEXCEPT {
    return y / mdl;
}

CONSTCD11
inline year_month_day_last
operator/(const month_day_last &mdl, int y) NOEXCEPT {
    return year(y) / mdl;
}

// year_month_weekday from operator/()

CONSTCD11
inline year_month_weekday
operator/(const year_month &ym, const weekday_indexed &wdi) NOEXCEPT {
    return {ym.year(), ym.month(), wdi};
}

CONSTCD11
inline year_month_weekday
operator/(const year &y, const month_weekday &mwd) NOEXCEPT {
    return {y, mwd.month(), mwd.weekday_indexed()};
}

CONSTCD11
inline year_month_weekday
operator/(int y, const month_weekday &mwd) NOEXCEPT {
    return year(y) / mwd;
}

CONSTCD11
inline year_month_weekday
operator/(const month_weekday &mwd, const year &y) NOEXCEPT {
    return y / mwd;
}

CONSTCD11
inline year_month_weekday
operator/(const month_weekday &mwd, int y) NOEXCEPT {
    return year(y) / mwd;
}

// year_month_weekday_last from operator/()

CONSTCD11
inline year_month_weekday_last
operator/(const year_month &ym, const weekday_last &wdl) NOEXCEPT {
    return {ym.year(), ym.month(), wdl};
}

CONSTCD11
inline year_month_weekday_last
operator/(const year &y, const month_weekday_last &mwdl) NOEXCEPT {
    return {y, mwdl.month(), mwdl.weekday_last()};
}

CONSTCD11
inline year_month_weekday_last
operator/(int y, const month_weekday_last &mwdl) NOEXCEPT {
    return year(y) / mwdl;
}

CONSTCD11
inline year_month_weekday_last
operator/(const month_weekday_last &mwdl, const year &y) NOEXCEPT {
    return y / mwdl;
}

CONSTCD11
inline year_month_weekday_last
operator/(const month_weekday_last &mwdl, int y) NOEXCEPT {
    return year(y) / mwdl;
}

template <class Duration>
struct fields;

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const fields<Duration> &fds, const std::string *abbrev = nullptr,
          const std::chrono::seconds *offset_sec = nullptr);

template <class CharT, class Traits, class Duration, class Alloc>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            fields<Duration> &fds, std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr);

// time_of_day

enum { am = 1,
       pm };

namespace detail {

// width<n>::value is the number of fractional decimal digits in 1/n
// width<0>::value and width<1>::value are defined to be 0
// If 1/n takes more than 18 fractional decimal digits,
//   the result is truncated to 19.
// Example:  width<2>::value    ==  1
// Example:  width<3>::value    == 19
// Example:  width<4>::value    ==  2
// Example:  width<10>::value   ==  1
// Example:  width<1000>::value ==  3
template <std::uint64_t n, std::uint64_t d = 10, unsigned w = 0,
          bool should_continue = !(n < 2) && d != 0 && (w < 19)>
struct width {
    static CONSTDATA unsigned value = 1 + width<n, d % n * 10, w + 1>::value;
};

template <std::uint64_t n, std::uint64_t d, unsigned w>
struct width<n, d, w, false> {
    static CONSTDATA unsigned value = 0;
};

template <unsigned exp>
struct static_pow10 {
  private:
    static CONSTDATA std::uint64_t h = static_pow10<exp / 2>::value;

  public:
    static CONSTDATA std::uint64_t value = h * h * (exp % 2 ? 10 : 1);
};

template <>
struct static_pow10<0> {
    static CONSTDATA std::uint64_t value = 1;
};

template <class Rep, unsigned w, bool in_range = (w < 19)>
struct make_precision {
    using type = std::chrono::duration<Rep,
                                       std::ratio<1, static_pow10<w>::value>>;
    static CONSTDATA unsigned width = w;
};

template <class Rep, unsigned w>
struct make_precision<Rep, w, false> {
    using type = std::chrono::duration<Rep, std::micro>;
    static CONSTDATA unsigned width = 6;
};

template <class Duration,
          unsigned w = width<std::common_type<
              Duration,
              std::chrono::seconds>::type::period::den>::value>
class decimal_format_seconds {
  public:
    using rep = typename std::common_type<Duration, std::chrono::seconds>::type::rep;
    using precision = typename make_precision<rep, w>::type;
    static auto CONSTDATA width = make_precision<rep, w>::width;

  private:
    std::chrono::seconds s_;
    precision sub_s_;

  public:
    CONSTCD11 decimal_format_seconds()
        : s_(), sub_s_() {}

    CONSTCD11 explicit decimal_format_seconds(const Duration &d) NOEXCEPT
        : s_(std::chrono::duration_cast<std::chrono::seconds>(d)),
          sub_s_(std::chrono::duration_cast<precision>(d - s_)) {}

    CONSTCD14 std::chrono::seconds &seconds() NOEXCEPT { return s_; }
    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT { return s_; }
    CONSTCD11 precision subseconds() const NOEXCEPT { return sub_s_; }

    CONSTCD14 precision to_duration() const NOEXCEPT {
        return s_ + sub_s_;
    }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        using namespace std::chrono;
        return sub_s_ < std::chrono::seconds{1} && s_ < minutes{1};
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const decimal_format_seconds &x) {
        date::detail::save_ostream<CharT, Traits> _(os);
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        os.width(2);
        os << x.s_.count() << std::use_facet<std::numpunct<char>>(os.getloc()).decimal_point();
        os.width(width);
        os << static_cast<std::int64_t>(x.sub_s_.count());
        return os;
    }
};

template <class Duration>
class decimal_format_seconds<Duration, 0> {
    static CONSTDATA unsigned w = 0;

  public:
    using rep = typename std::common_type<Duration, std::chrono::seconds>::type::rep;
    using precision = std::chrono::duration<rep>;
    static auto CONSTDATA width = make_precision<rep, w>::width;

  private:
    std::chrono::seconds s_;

  public:
    CONSTCD11 decimal_format_seconds() : s_() {}
    CONSTCD11 explicit decimal_format_seconds(const precision &s) NOEXCEPT
        : s_(s) {}

    CONSTCD14 std::chrono::seconds &seconds() NOEXCEPT { return s_; }
    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT { return s_; }
    CONSTCD14 precision to_duration() const NOEXCEPT { return s_; }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        using namespace std::chrono;
        return s_ < minutes{1};
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const decimal_format_seconds &x) {
        date::detail::save_ostream<CharT, Traits> _(os);
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        os.width(2);
        os << x.s_.count();
        return os;
    }
};

enum class classify {
    not_valid,
    hour,
    minute,
    second,
    subsecond
};

template <class Duration>
struct classify_duration {
    static CONSTDATA classify value =
        std::is_convertible<Duration, std::chrono::hours>::value
            ? classify::hour
            : std::is_convertible<Duration, std::chrono::minutes>::value
                  ? classify::minute
                  : std::is_convertible<Duration, std::chrono::seconds>::value
                        ? classify::second
                        : std::chrono::treat_as_floating_point<typename Duration::rep>::value
                              ? classify::not_valid
                              : classify::subsecond;
};

template <class Rep, class Period>
inline CONSTCD11
    typename std::enable_if<
        std::numeric_limits<Rep>::is_signed,
        std::chrono::duration<Rep, Period>>::type
    abs(std::chrono::duration<Rep, Period> d) {
    return d >= d.zero() ? +d : -d;
}

template <class Rep, class Period>
inline CONSTCD11
    typename std::enable_if<
        !std::numeric_limits<Rep>::is_signed,
        std::chrono::duration<Rep, Period>>::type
    abs(std::chrono::duration<Rep, Period> d) {
    return d;
}

class time_of_day_base {
  protected:
    std::chrono::hours h_;
    unsigned char mode_;
    bool neg_;

    enum { is24hr };

    CONSTCD11 time_of_day_base() NOEXCEPT
        : h_(0),
          mode_(static_cast<decltype(mode_)>(is24hr)),
          neg_(false) {}

    CONSTCD11 time_of_day_base(std::chrono::hours h, bool neg, unsigned m) NOEXCEPT
        : h_(detail::abs(h)),
          mode_(static_cast<decltype(mode_)>(m)),
          neg_(neg) {}

    CONSTCD14 void make24() NOEXCEPT;
    CONSTCD14 void make12() NOEXCEPT;

    CONSTCD14 std::chrono::hours to24hr() const;

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        return !neg_ && h_ < days{1};
    }
};

CONSTCD14
inline std::chrono::hours
time_of_day_base::to24hr() const {
    auto h = h_;
    if (mode_ == am || mode_ == pm) {
        CONSTDATA auto h12 = std::chrono::hours(12);
        if (mode_ == pm) {
            if (h != h12)
                h = h + h12;
        } else if (h == h12)
            h = std::chrono::hours(0);
    }
    return h;
}

CONSTCD14
inline void
time_of_day_base::make24() NOEXCEPT {
    h_ = to24hr();
    mode_ = is24hr;
}

CONSTCD14
inline void
time_of_day_base::make12() NOEXCEPT {
    if (mode_ == is24hr) {
        CONSTDATA auto h12 = std::chrono::hours(12);
        if (h_ >= h12) {
            if (h_ > h12)
                h_ = h_ - h12;
            mode_ = pm;
        } else {
            if (h_ == std::chrono::hours(0))
                h_ = h12;
            mode_ = am;
        }
    }
}

template <class Duration, detail::classify = detail::classify_duration<Duration>::value>
class time_of_day_storage;

template <class Rep, class Period>
class time_of_day_storage<std::chrono::duration<Rep, Period>, detail::classify::hour>
    : private detail::time_of_day_base {
    using base = detail::time_of_day_base;

  public:
    using precision = std::chrono::hours;

#if !defined(_MSC_VER) || _MSC_VER >= 1900
    CONSTCD11 time_of_day_storage() NOEXCEPT = default;
#else
    CONSTCD11 time_of_day_storage() = default;
#endif /* !defined(_MSC_VER) || _MSC_VER >= 1900 */

    CONSTCD11 explicit time_of_day_storage(std::chrono::hours since_midnight) NOEXCEPT
        : base(since_midnight, since_midnight < std::chrono::hours{0}, is24hr) {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::hours h, unsigned md) NOEXCEPT
        : base(h, h < std::chrono::hours{0}, md) {}

    CONSTCD11 std::chrono::hours hours() const NOEXCEPT { return h_; }
    CONSTCD11 unsigned mode() const NOEXCEPT { return mode_; }

    CONSTCD14 explicit operator precision() const NOEXCEPT {
        auto p = to24hr();
        if (neg_)
            p = -p;
        return p;
    }

    CONSTCD14 precision to_duration() const NOEXCEPT {
        return static_cast<precision>(*this);
    }

    CONSTCD14 time_of_day_storage &make24() NOEXCEPT {
        base::make24();
        return *this;
    }
    CONSTCD14 time_of_day_storage &make12() NOEXCEPT {
        base::make12();
        return *this;
    }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        return base::in_conventional_range();
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const time_of_day_storage &t) {
        using namespace std;
        detail::save_ostream<CharT, Traits> _(os);
        if (t.neg_)
            os << '-';
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        if (t.mode_ != am && t.mode_ != pm)
            os.width(2);
        os << t.h_.count();
        switch (t.mode_) {
            case time_of_day_storage::is24hr:
                os << "00";
                break;
            case am:
                os << "am";
                break;
            case pm:
                os << "pm";
                break;
        }
        return os;
    }
};

template <class Rep, class Period>
class time_of_day_storage<std::chrono::duration<Rep, Period>, detail::classify::minute>
    : private detail::time_of_day_base {
    using base = detail::time_of_day_base;

    std::chrono::minutes m_;

  public:
    using precision = std::chrono::minutes;

    CONSTCD11 time_of_day_storage() NOEXCEPT
        : base(),
          m_(0) {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::minutes since_midnight) NOEXCEPT
        : base(std::chrono::duration_cast<std::chrono::hours>(since_midnight),
               since_midnight < std::chrono::minutes{0}, is24hr),
          m_(detail::abs(since_midnight) - h_) {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::hours h, std::chrono::minutes m,
                                           unsigned md) NOEXCEPT
        : base(h, false, md),
          m_(m) {}

    CONSTCD11 std::chrono::hours hours() const NOEXCEPT { return h_; }
    CONSTCD11 std::chrono::minutes minutes() const NOEXCEPT { return m_; }
    CONSTCD11 unsigned mode() const NOEXCEPT { return mode_; }

    CONSTCD14 explicit operator precision() const NOEXCEPT {
        auto p = to24hr() + m_;
        if (neg_)
            p = -p;
        return p;
    }

    CONSTCD14 precision to_duration() const NOEXCEPT {
        return static_cast<precision>(*this);
    }

    CONSTCD14 time_of_day_storage &make24() NOEXCEPT {
        base::make24();
        return *this;
    }
    CONSTCD14 time_of_day_storage &make12() NOEXCEPT {
        base::make12();
        return *this;
    }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        return base::in_conventional_range() && m_ < std::chrono::hours{1};
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const time_of_day_storage &t) {
        using namespace std;
        detail::save_ostream<CharT, Traits> _(os);
        if (t.neg_)
            os << '-';
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        if (t.mode_ != am && t.mode_ != pm)
            os.width(2);
        os << t.h_.count() << ':';
        os.width(2);
        os << t.m_.count();
        switch (t.mode_) {
            case am:
                os << "am";
                break;
            case pm:
                os << "pm";
                break;
        }
        return os;
    }
};

template <class Rep, class Period>
class time_of_day_storage<std::chrono::duration<Rep, Period>, detail::classify::second>
    : private detail::time_of_day_base {
    using base = detail::time_of_day_base;
    using dfs = decimal_format_seconds<std::chrono::seconds>;

    std::chrono::minutes m_;
    dfs s_;

  public:
    using precision = std::chrono::seconds;

    CONSTCD11 time_of_day_storage() NOEXCEPT
        : base(),
          m_(0),
          s_() {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::seconds since_midnight) NOEXCEPT
        : base(std::chrono::duration_cast<std::chrono::hours>(since_midnight),
               since_midnight < std::chrono::seconds{0}, is24hr),
          m_(std::chrono::duration_cast<std::chrono::minutes>(detail::abs(since_midnight) - h_)),
          s_(detail::abs(since_midnight) - h_ - m_) {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::hours h, std::chrono::minutes m,
                                           std::chrono::seconds s, unsigned md) NOEXCEPT
        : base(h, false, md),
          m_(m),
          s_(s) {}

    CONSTCD11 std::chrono::hours hours() const NOEXCEPT { return h_; }
    CONSTCD11 std::chrono::minutes minutes() const NOEXCEPT { return m_; }
    CONSTCD14 std::chrono::seconds &seconds() NOEXCEPT { return s_.seconds(); }
    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT { return s_.seconds(); }
    CONSTCD11 unsigned mode() const NOEXCEPT { return mode_; }

    CONSTCD14 explicit operator precision() const NOEXCEPT {
        auto p = to24hr() + s_.to_duration() + m_;
        if (neg_)
            p = -p;
        return p;
    }

    CONSTCD14 precision to_duration() const NOEXCEPT {
        return static_cast<precision>(*this);
    }

    CONSTCD14 time_of_day_storage &make24() NOEXCEPT {
        base::make24();
        return *this;
    }
    CONSTCD14 time_of_day_storage &make12() NOEXCEPT {
        base::make12();
        return *this;
    }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        return base::in_conventional_range() && m_ < std::chrono::hours{1} &&
               s_.in_conventional_range();
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const time_of_day_storage &t) {
        using namespace std;
        detail::save_ostream<CharT, Traits> _(os);
        if (t.neg_)
            os << '-';
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        if (t.mode_ != am && t.mode_ != pm)
            os.width(2);
        os << t.h_.count() << ':';
        os.width(2);
        os << t.m_.count() << ':' << t.s_;
        switch (t.mode_) {
            case am:
                os << "am";
                break;
            case pm:
                os << "pm";
                break;
        }
        return os;
    }

    template <class CharT, class Traits, class Duration>
    friend std::basic_ostream<CharT, Traits> &
    date::to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
                    const fields<Duration> &fds, const std::string *abbrev,
                    const std::chrono::seconds *offset_sec);

    template <class CharT, class Traits, class Duration, class Alloc>
    friend std::basic_istream<CharT, Traits> &
    date::from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
                      fields<Duration> &fds,
                      std::basic_string<CharT, Traits, Alloc> *abbrev, std::chrono::minutes *offset);
};

template <class Rep, class Period>
class time_of_day_storage<std::chrono::duration<Rep, Period>, detail::classify::subsecond>
    : private detail::time_of_day_base {
  public:
    using Duration = std::chrono::duration<Rep, Period>;
    using dfs = decimal_format_seconds<typename std::common_type<Duration,
                                                                 std::chrono::seconds>::type>;
    using precision = typename dfs::precision;

  private:
    using base = detail::time_of_day_base;

    std::chrono::minutes m_;
    dfs s_;

  public:
    CONSTCD11 time_of_day_storage() NOEXCEPT
        : base(),
          m_(0),
          s_() {}

    CONSTCD11 explicit time_of_day_storage(Duration since_midnight) NOEXCEPT
        : base(date::trunc<std::chrono::hours>(since_midnight),
               since_midnight < Duration{0}, is24hr),
          m_(date::trunc<std::chrono::minutes>(detail::abs(since_midnight) - h_)),
          s_(detail::abs(since_midnight) - h_ - m_) {}

    CONSTCD11 explicit time_of_day_storage(std::chrono::hours h, std::chrono::minutes m,
                                           std::chrono::seconds s, precision sub_s,
                                           unsigned md) NOEXCEPT
        : base(h, false, md),
          m_(m),
          s_(s + sub_s) {}

    CONSTCD11 std::chrono::hours hours() const NOEXCEPT { return h_; }
    CONSTCD11 std::chrono::minutes minutes() const NOEXCEPT { return m_; }
    CONSTCD14 std::chrono::seconds &seconds() NOEXCEPT { return s_.seconds(); }
    CONSTCD11 std::chrono::seconds seconds() const NOEXCEPT { return s_.seconds(); }
    CONSTCD11 precision subseconds() const NOEXCEPT { return s_.subseconds(); }
    CONSTCD11 unsigned mode() const NOEXCEPT { return mode_; }

    CONSTCD14 explicit operator precision() const NOEXCEPT {
        auto p = to24hr() + s_.to_duration() + m_;
        if (neg_)
            p = -p;
        return p;
    }

    CONSTCD14 precision to_duration() const NOEXCEPT {
        return static_cast<precision>(*this);
    }

    CONSTCD14 time_of_day_storage &make24() NOEXCEPT {
        base::make24();
        return *this;
    }
    CONSTCD14 time_of_day_storage &make12() NOEXCEPT {
        base::make12();
        return *this;
    }

    CONSTCD11 bool in_conventional_range() const NOEXCEPT {
        return base::in_conventional_range() && m_ < std::chrono::hours{1} &&
               s_.in_conventional_range();
    }

    template <class CharT, class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const time_of_day_storage &t) {
        using namespace std;
        detail::save_ostream<CharT, Traits> _(os);
        if (t.neg_)
            os << '-';
        os.fill('0');
        os.flags(std::ios::dec | std::ios::right);
        if (t.mode_ != am && t.mode_ != pm)
            os.width(2);
        os << t.h_.count() << ':';
        os.width(2);
        os << t.m_.count() << ':' << t.s_;
        switch (t.mode_) {
            case am:
                os << "am";
                break;
            case pm:
                os << "pm";
                break;
        }
        return os;
    }

    template <class CharT, class Traits, class Duration>
    friend std::basic_ostream<CharT, Traits> &
    date::to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
                    const fields<Duration> &fds, const std::string *abbrev,
                    const std::chrono::seconds *offset_sec);

    template <class CharT, class Traits, class Duration, class Alloc>
    friend std::basic_istream<CharT, Traits> &
    date::from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
                      fields<Duration> &fds,
                      std::basic_string<CharT, Traits, Alloc> *abbrev, std::chrono::minutes *offset);
};

} // namespace detail

template <class Duration>
class time_of_day
    : public detail::time_of_day_storage<Duration> {
    using base = detail::time_of_day_storage<Duration>;

  public:
#if !defined(_MSC_VER) || _MSC_VER >= 1900
    CONSTCD11 time_of_day() NOEXCEPT = default;
#else
    CONSTCD11 time_of_day() = default;
#endif /* !defined(_MSC_VER) || _MSC_VER >= 1900 */

    CONSTCD11 explicit time_of_day(Duration since_midnight) NOEXCEPT
        : base(since_midnight) {}

    template <class Arg0, class Arg1, class... Args>
    CONSTCD11 explicit time_of_day(Arg0 &&arg0, Arg1 &&arg1, Args &&... args) NOEXCEPT
        : base(std::forward<Arg0>(arg0), std::forward<Arg1>(arg1), std::forward<Args>(args)...) {}
};

template <class Rep, class Period,
          class = typename std::enable_if<!std::chrono::treat_as_floating_point<Rep>::value>::type>
CONSTCD11 inline time_of_day<std::chrono::duration<Rep, Period>>
make_time(const std::chrono::duration<Rep, Period> &d) {
    return time_of_day<std::chrono::duration<Rep, Period>>(d);
}

CONSTCD11
inline time_of_day<std::chrono::hours>
make_time(const std::chrono::hours &h, unsigned md) {
    return time_of_day<std::chrono::hours>(h, md);
}

CONSTCD11
inline time_of_day<std::chrono::minutes>
make_time(const std::chrono::hours &h, const std::chrono::minutes &m,
          unsigned md) {
    return time_of_day<std::chrono::minutes>(h, m, md);
}

CONSTCD11
inline time_of_day<std::chrono::seconds>
make_time(const std::chrono::hours &h, const std::chrono::minutes &m,
          const std::chrono::seconds &s, unsigned md) {
    return time_of_day<std::chrono::seconds>(h, m, s, md);
}

template <class Rep, class Period,
          class = typename std::enable_if<std::ratio_less<Period,
                                                          std::ratio<1>>::value>::type>
CONSTCD11 inline time_of_day<std::chrono::duration<Rep, Period>>
make_time(const std::chrono::hours &h, const std::chrono::minutes &m,
          const std::chrono::seconds &s, const std::chrono::duration<Rep, Period> &sub_s,
          unsigned md) {
    return time_of_day<std::chrono::duration<Rep, Period>>(h, m, s, sub_s, md);
}

template <class CharT, class Traits, class Duration>
inline
    typename std::enable_if<
        !std::chrono::treat_as_floating_point<typename Duration::rep>::value &&
            std::ratio_less<typename Duration::period, days::period>::value,
        std::basic_ostream<CharT, Traits> &>::type
    operator<<(std::basic_ostream<CharT, Traits> &os, const sys_time<Duration> &tp) {
    auto const dp = date::floor<days>(tp);
    return os << year_month_day(dp) << ' ' << make_time(tp - dp);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const sys_days &dp) {
    return os << year_month_day(dp);
}

template <class CharT, class Traits, class Duration>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os, const local_time<Duration> &ut) {
    return (os << sys_time<Duration>{ut.time_since_epoch()});
}

// to_stream

CONSTDATA year nanyear{-32768};

template <class Duration>
struct fields {
    year_month_day ymd{nanyear / 0 / 0};
    weekday wd{8u};
    time_of_day<Duration> tod{};
    bool has_tod = false;

    fields() = default;

    fields(year_month_day ymd_) : ymd(ymd_) {}
    fields(weekday wd_) : wd(wd_) {}
    fields(time_of_day<Duration> tod_) : tod(tod_), has_tod(true) {}

    fields(year_month_day ymd_, weekday wd_) : ymd(ymd_), wd(wd_) {}
    fields(year_month_day ymd_, time_of_day<Duration> tod_) : ymd(ymd_), tod(tod_),
                                                              has_tod(true) {}

    fields(weekday wd_, time_of_day<Duration> tod_) : wd(wd_), tod(tod_), has_tod(true) {}

    fields(year_month_day ymd_, weekday wd_, time_of_day<Duration> tod_)
        : ymd(ymd_), wd(wd_), tod(tod_), has_tod(true) {}
};

namespace detail {

template <class CharT, class Traits, class Duration>
unsigned
extract_weekday(std::basic_ostream<CharT, Traits> &os, const fields<Duration> &fds) {
    if (!fds.ymd.ok() && !fds.wd.ok()) {
        // fds does not contain a valid weekday
        os.setstate(std::ios::failbit);
        return 8;
    }
    weekday wd;
    if (fds.ymd.ok()) {
        wd = weekday{sys_days(fds.ymd)};
        if (fds.wd.ok() && wd != fds.wd) {
            // fds.ymd and fds.wd are inconsistent
            os.setstate(std::ios::failbit);
            return 8;
        }
    } else
        wd = fds.wd;
    return static_cast<unsigned>((wd - Sunday).count());
}

template <class CharT, class Traits, class Duration>
unsigned
extract_month(std::basic_ostream<CharT, Traits> &os, const fields<Duration> &fds) {
    if (!fds.ymd.month().ok()) {
        // fds does not contain a valid month
        os.setstate(std::ios::failbit);
        return 0;
    }
    return static_cast<unsigned>(fds.ymd.month());
}

} // namespace detail

#if ONLY_C_LOCALE

namespace detail {

inline std::pair<const std::string *, const std::string *>
weekday_names() {
    using namespace std;
    static const string nm[] =
        {
            "Sunday",
            "Monday",
            "Tuesday",
            "Wednesday",
            "Thursday",
            "Friday",
            "Saturday",
            "Sun",
            "Mon",
            "Tue",
            "Wed",
            "Thu",
            "Fri",
            "Sat"};
    return make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

inline std::pair<const std::string *, const std::string *>
month_names() {
    using namespace std;
    static const string nm[] =
        {
            "January",
            "February",
            "March",
            "April",
            "May",
            "June",
            "July",
            "August",
            "September",
            "October",
            "November",
            "December",
            "Jan",
            "Feb",
            "Mar",
            "Apr",
            "May",
            "Jun",
            "Jul",
            "Aug",
            "Sep",
            "Oct",
            "Nov",
            "Dec"};
    return make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

inline std::pair<const std::string *, const std::string *>
ampm_names() {
    using namespace std;
    static const string nm[] =
        {
            "AM",
            "PM"};
    return make_pair(nm, nm + sizeof(nm) / sizeof(nm[0]));
}

template <class CharT, class Traits, class FwdIter>
FwdIter
scan_keyword(std::basic_istream<CharT, Traits> &is, FwdIter kb, FwdIter ke) {
    using namespace std;
    size_t nkw = static_cast<size_t>(std::distance(kb, ke));
    const unsigned char doesnt_match = '\0';
    const unsigned char might_match = '\1';
    const unsigned char does_match = '\2';
    unsigned char statbuf[100];
    unsigned char *status = statbuf;
    unique_ptr<unsigned char, void (*)(void *)> stat_hold(0, free);
    if (nkw > sizeof(statbuf)) {
        status = (unsigned char *) malloc(nkw);
        if (status == nullptr)
            throw bad_alloc();
        stat_hold.reset(status);
    }
    size_t n_might_match = nkw; // At this point, any keyword might match
    size_t n_does_match = 0;    // but none of them definitely do
    // Initialize all statuses to might_match, except for "" keywords are does_match
    unsigned char *st = status;
    for (auto ky = kb; ky != ke; ++ky, ++st) {
        if (!ky->empty())
            *st = might_match;
        else {
            *st = does_match;
            --n_might_match;
            ++n_does_match;
        }
    }
    // While there might be a match, tests keywords against the next CharT
    for (size_t indx = 0; is && n_might_match > 0; ++indx) {
        // Peek at the next CharT but don't consume it
        auto ic = is.peek();
        if (ic == EOF) {
            is.setstate(ios::eofbit);
            break;
        }
        auto c = static_cast<char>(toupper(ic));
        bool consume = false;
        // For each keyword which might match, see if the indx character is c
        // If a match if found, consume c
        // If a match is found, and that is the last character in the keyword,
        //    then that keyword matches.
        // If the keyword doesn't match this character, then change the keyword
        //    to doesn't match
        st = status;
        for (auto ky = kb; ky != ke; ++ky, ++st) {
            if (*st == might_match) {
                if (c == static_cast<char>(toupper((*ky)[indx]))) {
                    consume = true;
                    if (ky->size() == indx + 1) {
                        *st = does_match;
                        --n_might_match;
                        ++n_does_match;
                    }
                } else {
                    *st = doesnt_match;
                    --n_might_match;
                }
            }
        }
        // consume if we matched a character
        if (consume) {
            (void) is.get();
            // If we consumed a character and there might be a matched keyword that
            //   was marked matched on a previous iteration, then such keywords
            //   are now marked as not matching.
            if (n_might_match + n_does_match > 1) {
                st = status;
                for (auto ky = kb; ky != ke; ++ky, ++st) {
                    if (*st == does_match && ky->size() != indx + 1) {
                        *st = doesnt_match;
                        --n_does_match;
                    }
                }
            }
        }
    }
    // We've exited the loop because we hit eof and/or we have no more "might matches".
    // Return the first matching result
    for (st = status; kb != ke; ++kb, ++st)
        if (*st == does_match)
            break;
    if (kb == ke)
        is.setstate(ios_base::failbit);
    return kb;
}

} // namespace detail

#endif // ONLY_C_LOCALE

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const fields<Duration> &fds, const std::string *abbrev,
          const std::chrono::seconds *offset_sec) {
    using namespace std;
    using namespace std::chrono;
    using namespace detail;
    date::detail::save_ostream<CharT, Traits> ss(os);
    os.fill(' ');
    os.flags(std::ios::skipws | std::ios::dec);
    os.width(0);
    tm tm{};
    bool insert_negative = fds.has_tod && fds.tod.to_duration() < Duration::zero();
#if !ONLY_C_LOCALE
    auto &facet = use_facet<time_put<CharT>>(os.getloc());
#endif
    const CharT *command = nullptr;
    CharT modified = CharT{};
    for (; *fmt; ++fmt) {
        switch (*fmt) {
            case 'a':
            case 'A':
                if (command) {
                    if (modified == CharT{}) {
                        tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
                        if (os.fail())
                            return os;
#if !ONLY_C_LOCALE
                        const CharT f[] = {'%', *fmt};
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
#else  // ONLY_C_LOCALE
                        os << weekday_names().first[tm.tm_wday + 7 * (*fmt == 'a')];
#endif // ONLY_C_LOCALE
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'b':
            case 'B':
            case 'h':
                if (command) {
                    if (modified == CharT{}) {
                        tm.tm_mon = static_cast<int>(extract_month(os, fds)) - 1;
#if !ONLY_C_LOCALE
                        const CharT f[] = {'%', *fmt};
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
#else  // ONLY_C_LOCALE
                        os << month_names().first[tm.tm_mon + 12 * (*fmt != 'B')];
#endif // ONLY_C_LOCALE
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'c':
            case 'x':
                if (command) {
                    if (modified == CharT{'O'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        if (*fmt == 'c' && !fds.has_tod)
                            os.setstate(std::ios::failbit);
#if !ONLY_C_LOCALE
                        tm = std::tm{};
                        auto const &ymd = fds.ymd;
                        auto ld = local_days(ymd);
                        if (*fmt == 'c') {
                            tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
                            tm.tm_min = static_cast<int>(fds.tod.minutes().count());
                            tm.tm_hour = static_cast<int>(fds.tod.hours().count());
                        }
                        tm.tm_mday = static_cast<int>(static_cast<unsigned>(ymd.day()));
                        tm.tm_mon = static_cast<int>(extract_month(os, fds) - 1);
                        tm.tm_year = static_cast<int>(ymd.year()) - 1900;
                        tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
                        if (os.fail())
                            return os;
                        tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
                        CharT f[3] = {'%'};
                        auto fe = begin(f) + 1;
                        if (modified == CharT{'E'})
                            *fe++ = modified;
                        *fe++ = *fmt;
                        facet.put(os, os, os.fill(), &tm, begin(f), fe);
#else  // ONLY_C_LOCALE
                        if (*fmt == 'c') {
                            auto wd = static_cast<int>(extract_weekday(os, fds));
                            os << weekday_names().first[static_cast<unsigned>(wd) + 7]
                               << ' ';
                            os << month_names().first[extract_month(os, fds) - 1 + 12] << ' ';
                            auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
                            if (d < 10)
                                os << ' ';
                            os << d << ' '
                               << make_time(duration_cast<seconds>(fds.tod.to_duration()))
                               << ' ' << fds.ymd.year();

                        } else // *fmt == 'x'
                        {
                            auto const &ymd = fds.ymd;
                            save_ostream<CharT, Traits> _(os);
                            os.fill('0');
                            os.flags(std::ios::dec | std::ios::right);
                            os.width(2);
                            os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
                            os.width(2);
                            os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
                            os.width(2);
                            os << static_cast<int>(ymd.year()) % 100;
                        }
#endif // ONLY_C_LOCALE
                    }
                    command = nullptr;
                    modified = CharT{};
                } else
                    os << *fmt;
                break;
            case 'C':
                if (command) {
                    if (modified == CharT{'O'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.year().ok())
                            os.setstate(std::ios::failbit);
                        auto y = static_cast<int>(fds.ymd.year());
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            save_ostream<CharT, Traits> _(os);
                            os.fill('0');
                            os.flags(std::ios::dec | std::ios::right);
                            if (y >= 0) {
                                os.width(2);
                                os << y / 100;
                            } else {
                                os << CharT{'-'};
                                os.width(2);
                                os << -(y - 99) / 100;
                            }
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'E'}) {
                            tm.tm_year = y - 1900;
                            CharT f[3] = {'%', 'E', 'C'};
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    command = nullptr;
                    modified = CharT{};
                } else
                    os << *fmt;
                break;
            case 'd':
            case 'e':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.day().ok())
                            os.setstate(std::ios::failbit);
                        auto d = static_cast<int>(static_cast<unsigned>(fds.ymd.day()));
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            save_ostream<CharT, Traits> _(os);
                            if (*fmt == CharT{'d'})
                                os.fill('0');
                            else
                                os.fill(' ');
                            os.flags(std::ios::dec | std::ios::right);
                            os.width(2);
                            os << d;
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            tm.tm_mday = d;
                            CharT f[3] = {'%', 'O', *fmt};
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    command = nullptr;
                    modified = CharT{};
                } else
                    os << *fmt;
                break;
            case 'D':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto const &ymd = fds.ymd;
                        save_ostream<CharT, Traits> _(os);
                        os.fill('0');
                        os.flags(std::ios::dec | std::ios::right);
                        os.width(2);
                        os << static_cast<unsigned>(ymd.month()) << CharT{'/'};
                        os.width(2);
                        os << static_cast<unsigned>(ymd.day()) << CharT{'/'};
                        os.width(2);
                        os << static_cast<int>(ymd.year()) % 100;
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'F':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto const &ymd = fds.ymd;
                        save_ostream<CharT, Traits> _(os);
                        os.fill('0');
                        os.flags(std::ios::dec | std::ios::right);
                        os.width(4);
                        os << static_cast<int>(ymd.year()) << CharT{'-'};
                        os.width(2);
                        os << static_cast<unsigned>(ymd.month()) << CharT{'-'};
                        os.width(2);
                        os << static_cast<unsigned>(ymd.day());
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'g':
            case 'G':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto ld = local_days(fds.ymd);
                        auto y = year_month_day{ld + days{3}}.year();
                        auto start = local_days((y - years{1}) / December / Thursday[last]) +
                                     (Monday - Thursday);
                        if (ld < start)
                            --y;
                        if (*fmt == CharT{'G'})
                            os << y;
                        else {
                            save_ostream<CharT, Traits> _(os);
                            os.fill('0');
                            os.flags(std::ios::dec | std::ios::right);
                            os.width(2);
                            os << std::abs(static_cast<int>(y)) % 100;
                        }
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'H':
            case 'I':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
                        if (insert_negative) {
                            os << '-';
                            insert_negative = false;
                        }
                        auto hms = fds.tod;
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            if (*fmt == CharT{'I'})
                                hms.make12();
                            if (hms.hours() < hours{10})
                                os << CharT{'0'};
                            os << hms.hours().count();
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_hour = static_cast<int>(hms.hours().count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'j':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto ld = local_days(fds.ymd);
                        auto y = fds.ymd.year();
                        auto doy = ld - local_days(y / January / 1) + days{1};
                        save_ostream<CharT, Traits> _(os);
                        os.fill('0');
                        os.flags(std::ios::dec | std::ios::right);
                        os.width(3);
                        os << doy.count();
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'm':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.month().ok())
                            os.setstate(std::ios::failbit);
                        auto m = static_cast<unsigned>(fds.ymd.month());
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            if (m < 10)
                                os << CharT{'0'};
                            os << m;
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_mon = static_cast<int>(m - 1);
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'M':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
                        if (insert_negative) {
                            os << '-';
                            insert_negative = false;
                        }
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            if (fds.tod.minutes() < minutes{10})
                                os << CharT{'0'};
                            os << fds.tod.minutes().count();
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_min = static_cast<int>(fds.tod.minutes().count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'n':
                if (command) {
                    if (modified == CharT{})
                        os << CharT{'\n'};
                    else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'p':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
#if !ONLY_C_LOCALE
                        const CharT f[] = {'%', *fmt};
                        tm.tm_hour = static_cast<int>(fds.tod.hours().count());
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
#else
                        if (fds.tod.hours() < hours{12})
                            os << ampm_names().first[0];
                        else
                            os << ampm_names().first[1];
#endif
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'r':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
#if !ONLY_C_LOCALE
                        const CharT f[] = {'%', *fmt};
                        tm.tm_hour = static_cast<int>(fds.tod.hours().count());
                        tm.tm_min = static_cast<int>(fds.tod.minutes().count());
                        tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
#else
                        time_of_day<seconds> tod(duration_cast<seconds>(fds.tod.to_duration()));
                        tod.make12();
                        save_ostream<CharT, Traits> _(os);
                        os.fill('0');
                        os.width(2);
                        os << tod.hours().count() << CharT{':'};
                        os.width(2);
                        os << tod.minutes().count() << CharT{':'};
                        os.width(2);
                        os << tod.seconds().count() << CharT{' '};
                        tod.make24();
                        if (tod.hours() < hours{12})
                            os << ampm_names().first[0];
                        else
                            os << ampm_names().first[1];
#endif
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'R':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
                        if (fds.tod.hours() < hours{10})
                            os << CharT{'0'};
                        os << fds.tod.hours().count() << CharT{':'};
                        if (fds.tod.minutes() < minutes{10})
                            os << CharT{'0'};
                        os << fds.tod.minutes().count();
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'S':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
                        if (insert_negative) {
                            os << '-';
                            insert_negative = false;
                        }
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            os << fds.tod.s_;
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_sec = static_cast<int>(fds.tod.s_.seconds().count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 't':
                if (command) {
                    if (modified == CharT{})
                        os << CharT{'\t'};
                    else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'T':
                if (command) {
                    if (modified == CharT{}) {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
                        os << fds.tod;
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'u':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        auto wd = extract_weekday(os, fds);
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            os << (wd != 0 ? wd : 7u);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_wday = static_cast<int>(wd);
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'U':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        auto const &ymd = fds.ymd;
                        if (!ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto ld = local_days(ymd);
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            auto st = local_days(Sunday[1] / January / ymd.year());
                            if (ld < st)
                                os << CharT{'0'} << CharT{'0'};
                            else {
                                auto wn = duration_cast<weeks>(ld - st).count() + 1;
                                if (wn < 10)
                                    os << CharT{'0'};
                                os << wn;
                            }
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
                            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
                            if (os.fail())
                                return os;
                            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'V':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto ld = local_days(fds.ymd);
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            auto y = year_month_day{ld + days{3}}.year();
                            auto st = local_days((y - years{1}) / 12 / Thursday[last]) +
                                      (Monday - Thursday);
                            if (ld < st) {
                                --y;
                                st = local_days((y - years{1}) / 12 / Thursday[last]) +
                                     (Monday - Thursday);
                            }
                            auto wn = duration_cast<weeks>(ld - st).count() + 1;
                            if (wn < 10)
                                os << CharT{'0'};
                            os << wn;
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            auto const &ymd = fds.ymd;
                            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
                            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
                            if (os.fail())
                                return os;
                            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'w':
                if (command) {
                    auto wd = extract_weekday(os, fds);
                    if (os.fail())
                        return os;
#if !ONLY_C_LOCALE
                    if (modified == CharT{})
#else
                    if (modified != CharT{'E'})
#endif
                    {
                        os << wd;
                    }
#if !ONLY_C_LOCALE
                    else if (modified == CharT{'O'}) {
                        const CharT f[] = {'%', modified, *fmt};
                        tm.tm_wday = static_cast<int>(wd);
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                    }
#endif
                    else {
                        os << CharT{'%'} << modified << *fmt;
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'W':
                if (command) {
                    if (modified == CharT{'E'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        auto const &ymd = fds.ymd;
                        if (!ymd.ok())
                            os.setstate(std::ios::failbit);
                        auto ld = local_days(ymd);
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            auto st = local_days(Monday[1] / January / ymd.year());
                            if (ld < st)
                                os << CharT{'0'} << CharT{'0'};
                            else {
                                auto wn = duration_cast<weeks>(ld - st).count() + 1;
                                if (wn < 10)
                                    os << CharT{'0'};
                                os << wn;
                            }
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_year = static_cast<int>(ymd.year()) - 1900;
                            tm.tm_wday = static_cast<int>(extract_weekday(os, fds));
                            if (os.fail())
                                return os;
                            tm.tm_yday = static_cast<int>((ld - local_days(ymd.year() / 1 / 1)).count());
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'X':
                if (command) {
                    if (modified == CharT{'O'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.has_tod)
                            os.setstate(std::ios::failbit);
#if !ONLY_C_LOCALE
                        tm = std::tm{};
                        tm.tm_sec = static_cast<int>(fds.tod.seconds().count());
                        tm.tm_min = static_cast<int>(fds.tod.minutes().count());
                        tm.tm_hour = static_cast<int>(fds.tod.hours().count());
                        CharT f[3] = {'%'};
                        auto fe = begin(f) + 1;
                        if (modified == CharT{'E'})
                            *fe++ = modified;
                        *fe++ = *fmt;
                        facet.put(os, os, os.fill(), &tm, begin(f), fe);
#else
                        os << fds.tod;
#endif
                    }
                    command = nullptr;
                    modified = CharT{};
                } else
                    os << *fmt;
                break;
            case 'y':
                if (command) {
                    if (!fds.ymd.year().ok())
                        os.setstate(std::ios::failbit);
                    auto y = static_cast<int>(fds.ymd.year());
#if !ONLY_C_LOCALE
                    if (modified == CharT{}) {
#endif
                        y = std::abs(y) % 100;
                        if (y < 10)
                            os << CharT{'0'};
                        os << y;
#if !ONLY_C_LOCALE
                    } else {
                        const CharT f[] = {'%', modified, *fmt};
                        tm.tm_year = y - 1900;
                        facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                    }
#endif
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'Y':
                if (command) {
                    if (modified == CharT{'O'})
                        os << CharT{'%'} << modified << *fmt;
                    else {
                        if (!fds.ymd.year().ok())
                            os.setstate(std::ios::failbit);
                        auto y = fds.ymd.year();
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            os << y;
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'E'}) {
                            const CharT f[] = {'%', modified, *fmt};
                            tm.tm_year = static_cast<int>(y) - 1900;
                            facet.put(os, os, os.fill(), &tm, begin(f), end(f));
                        }
#endif
                    }
                    modified = CharT{};
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'z':
                if (command) {
                    if (offset_sec == nullptr) {
                        // Can not format %z with unknown offset
                        os.setstate(ios::failbit);
                        return os;
                    }
                    auto m = duration_cast<minutes>(*offset_sec);
                    auto neg = m < minutes{0};
                    m = date::abs(m);
                    auto h = duration_cast<hours>(m);
                    m -= h;
                    if (neg)
                        os << CharT{'-'};
                    else
                        os << CharT{'+'};
                    if (h < hours{10})
                        os << CharT{'0'};
                    os << h.count();
                    if (modified != CharT{})
                        os << CharT{':'};
                    if (m < minutes{10})
                        os << CharT{'0'};
                    os << m.count();
                    command = nullptr;
                    modified = CharT{};
                } else
                    os << *fmt;
                break;
            case 'Z':
                if (command) {
                    if (modified == CharT{}) {
                        if (abbrev == nullptr) {
                            // Can not format %Z with unknown time_zone
                            os.setstate(ios::failbit);
                            return os;
                        }
                        for (auto c : *abbrev)
                            os << CharT(c);
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        modified = CharT{};
                    }
                    command = nullptr;
                } else
                    os << *fmt;
                break;
            case 'E':
            case 'O':
                if (command) {
                    if (modified == CharT{}) {
                        modified = *fmt;
                    } else {
                        os << CharT{'%'} << modified << *fmt;
                        command = nullptr;
                        modified = CharT{};
                    }
                } else
                    os << *fmt;
                break;
            case '%':
                if (command) {
                    if (modified == CharT{}) {
                        os << CharT{'%'};
                        command = nullptr;
                    } else {
                        os << CharT{'%'} << modified << CharT{'%'};
                        command = nullptr;
                        modified = CharT{};
                    }
                } else
                    command = fmt;
                break;
            default:
                if (command) {
                    os << CharT{'%'};
                    command = nullptr;
                }
                if (modified != CharT{}) {
                    os << modified;
                    modified = CharT{};
                }
                os << *fmt;
                break;
        }
    }
    if (command)
        os << CharT{'%'};
    if (modified != CharT{})
        os << modified;
    return os;
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const year &y) {
    using CT = std::chrono::seconds;
    fields<CT> fds{y / 0 / 0};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const month &m) {
    using CT = std::chrono::seconds;
    fields<CT> fds{m / 0 / nanyear};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const day &d) {
    using CT = std::chrono::seconds;
    fields<CT> fds{d / 0 / nanyear};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const weekday &wd) {
    using CT = std::chrono::seconds;
    fields<CT> fds{wd};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const year_month &ym) {
    using CT = std::chrono::seconds;
    fields<CT> fds{ym / 0};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt, const month_day &md) {
    using CT = std::chrono::seconds;
    fields<CT> fds{md / nanyear};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const year_month_day &ymd) {
    using CT = std::chrono::seconds;
    fields<CT> fds{ymd};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits, class Rep, class Period>
inline std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const std::chrono::duration<Rep, Period> &d) {
    using Duration = std::chrono::duration<Rep, Period>;
    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
    fields<CT> fds{time_of_day<CT>{d}};
    return to_stream(os, fmt, fds);
}

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const local_time<Duration> &tp, const std::string *abbrev = nullptr,
          const std::chrono::seconds *offset_sec = nullptr) {
    using CT = typename std::common_type<Duration, std::chrono::seconds>::type;
    auto ld = floor<days>(tp);
    fields<CT> fds{year_month_day{ld}, time_of_day<CT>{tp - local_seconds{ld}}};
    return to_stream(os, fmt, fds, abbrev, offset_sec);
}

template <class CharT, class Traits, class Duration>
std::basic_ostream<CharT, Traits> &
to_stream(std::basic_ostream<CharT, Traits> &os, const CharT *fmt,
          const sys_time<Duration> &tp) {
    using namespace std::chrono;
    using CT = typename std::common_type<Duration, seconds>::type;
    const std::string abbrev("UTC");
    CONSTDATA seconds offset{0};
    auto sd = floor<days>(tp);
    fields<CT> fds{year_month_day{sd}, time_of_day<CT>{tp - sys_seconds{sd}}};
    return to_stream(os, fmt, fds, &abbrev, &offset);
}

// format

template <class CharT, class Streamable>
auto format(const std::locale &loc, const CharT *fmt, const Streamable &tp)
    -> decltype(to_stream(std::declval<std::basic_ostream<CharT> &>(), fmt, tp),
                std::basic_string<CharT>{}) {
    std::basic_ostringstream<CharT> os;
    os.exceptions(std::ios::failbit | std::ios::badbit);
    os.imbue(loc);
    to_stream(os, fmt, tp);
    return os.str();
}

template <class CharT, class Streamable>
auto format(const CharT *fmt, const Streamable &tp)
    -> decltype(to_stream(std::declval<std::basic_ostream<CharT> &>(), fmt, tp),
                std::basic_string<CharT>{}) {
    std::basic_ostringstream<CharT> os;
    os.exceptions(std::ios::failbit | std::ios::badbit);
    to_stream(os, fmt, tp);
    return os.str();
}

template <class CharT, class Traits, class Alloc, class Streamable>
auto format(const std::locale &loc, const std::basic_string<CharT, Traits, Alloc> &fmt,
            const Streamable &tp)
    -> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits> &>(), fmt.c_str(), tp),
                std::basic_string<CharT, Traits, Alloc>{}) {
    std::basic_ostringstream<CharT, Traits, Alloc> os;
    os.exceptions(std::ios::failbit | std::ios::badbit);
    os.imbue(loc);
    to_stream(os, fmt.c_str(), tp);
    return os.str();
}

template <class CharT, class Traits, class Alloc, class Streamable>
auto format(const std::basic_string<CharT, Traits, Alloc> &fmt, const Streamable &tp)
    -> decltype(to_stream(std::declval<std::basic_ostream<CharT, Traits> &>(), fmt.c_str(), tp),
                std::basic_string<CharT, Traits, Alloc>{}) {
    std::basic_ostringstream<CharT, Traits, Alloc> os;
    os.exceptions(std::ios::failbit | std::ios::badbit);
    to_stream(os, fmt.c_str(), tp);
    return os.str();
}

// parse

namespace detail {

template <class CharT, class Traits>
bool read_char(std::basic_istream<CharT, Traits> &is, CharT fmt, std::ios::iostate &err) {
    auto ic = is.get();
    if (Traits::eq_int_type(ic, Traits::eof()) ||
        !Traits::eq(Traits::to_char_type(ic), fmt)) {
        err |= std::ios::failbit;
        is.setstate(std::ios::failbit);
        return false;
    }
    return true;
}

template <class CharT, class Traits>
unsigned
read_unsigned(std::basic_istream<CharT, Traits> &is, unsigned m = 1, unsigned M = 10) {
    unsigned x = 0;
    unsigned count = 0;
    while (true) {
        auto ic = is.peek();
        if (Traits::eq_int_type(ic, Traits::eof()))
            break;
        auto c = static_cast<char>(Traits::to_char_type(ic));
        if (!('0' <= c && c <= '9'))
            break;
        (void) is.get();
        ++count;
        x = 10 * x + static_cast<unsigned>(c - '0');
        if (count == M)
            break;
    }
    if (count < m)
        is.setstate(std::ios::failbit);
    return x;
}

template <class CharT, class Traits>
int read_signed(std::basic_istream<CharT, Traits> &is, unsigned m = 1, unsigned M = 10) {
    auto ic = is.peek();
    if (!Traits::eq_int_type(ic, Traits::eof())) {
        auto c = static_cast<char>(Traits::to_char_type(ic));
        if (('0' <= c && c <= '9') || c == '-' || c == '+') {
            if (c == '-' || c == '+')
                (void) is.get();
            auto x = static_cast<int>(read_unsigned(is, std::max(m, 1u), M));
            if (!is.fail()) {
                if (c == '-')
                    x = -x;
                return x;
            }
        }
    }
    if (m > 0)
        is.setstate(std::ios::failbit);
    return 0;
}

template <class CharT, class Traits>
long double
read_long_double(std::basic_istream<CharT, Traits> &is, unsigned m = 1, unsigned M = 10) {
    using namespace std;
    unsigned count = 0;
    auto decimal_point = Traits::to_int_type(
        use_facet<numpunct<CharT>>(is.getloc()).decimal_point());
    std::string buf;
    while (true) {
        auto ic = is.peek();
        if (Traits::eq_int_type(ic, Traits::eof()))
            break;
        if (Traits::eq_int_type(ic, decimal_point)) {
            buf += '.';
            decimal_point = Traits::eof();
            is.get();
        } else {
            auto c = static_cast<char>(Traits::to_char_type(ic));
            if (!('0' <= c && c <= '9'))
                break;
            buf += c;
            (void) is.get();
        }
        if (++count == M)
            break;
    }
    if (count < m) {
        is.setstate(std::ios::failbit);
        return 0;
    }
    return std::stold(buf);
}

struct rs {
    int &i;
    unsigned m;
    unsigned M;
};

struct ru {
    int &i;
    unsigned m;
    unsigned M;
};

struct rld {
    long double &i;
    unsigned m;
    unsigned M;
};

template <class CharT, class Traits>
void read(std::basic_istream<CharT, Traits> &) {
}

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, CharT a0, Args &&... args);

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, rs a0, Args &&... args);

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, ru a0, Args &&... args);

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, int a0, Args &&... args);

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, rld a0, Args &&... args);

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, CharT a0, Args &&... args) {
    // No-op if a0 == CharT{}
    if (a0 != CharT{}) {
        auto ic = is.peek();
        if (Traits::eq_int_type(ic, Traits::eof())) {
            is.setstate(std::ios::failbit | std::ios::eofbit);
            return;
        }
        if (!Traits::eq(Traits::to_char_type(ic), a0)) {
            is.setstate(std::ios::failbit);
            return;
        }
        (void) is.get();
    }
    read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, rs a0, Args &&... args) {
    auto x = read_signed(is, a0.m, a0.M);
    if (is.fail())
        return;
    a0.i = x;
    read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, ru a0, Args &&... args) {
    auto x = read_unsigned(is, a0.m, a0.M);
    if (is.fail())
        return;
    a0.i = static_cast<int>(x);
    read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, int a0, Args &&... args) {
    if (a0 != -1) {
        auto u = static_cast<unsigned>(a0);
        CharT buf[std::numeric_limits<unsigned>::digits10 + 2] = {};
        auto e = buf;
        do {
            *e++ = CharT(u % 10) + CharT{'0'};
            u /= 10;
        } while (u > 0);
        std::reverse(buf, e);
        for (auto p = buf; p != e && is.rdstate() == std::ios::goodbit; ++p)
            read(is, *p);
    }
    if (is.rdstate() == std::ios::goodbit)
        read(is, std::forward<Args>(args)...);
}

template <class CharT, class Traits, class... Args>
void read(std::basic_istream<CharT, Traits> &is, rld a0, Args &&... args) {
    auto x = read_long_double(is, a0.m, a0.M);
    if (is.fail())
        return;
    a0.i = x;
    read(is, std::forward<Args>(args)...);
}

template <class T, class CharT, class Traits>
inline void
checked_set(T &value, T from, T not_a_value, std::basic_ios<CharT, Traits> &is) {
    if (!is.fail()) {
        if (value == not_a_value)
            value = std::move(from);
        else if (value != from)
            is.setstate(std::ios::failbit);
    }
}

} // namespace detail

template <class CharT, class Traits, class Duration, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            fields<Duration> &fds, std::basic_string<CharT, Traits, Alloc> *abbrev,
            std::chrono::minutes *offset) {
    using namespace std;
    using namespace std::chrono;
    typename basic_istream<CharT, Traits>::sentry ok{is, true};
    if (ok) {
        date::detail::save_istream<CharT, Traits> ss(is);
        is.fill(' ');
        is.flags(std::ios::skipws | std::ios::dec);
        is.width(0);
#if !ONLY_C_LOCALE
        auto &f = use_facet<time_get<CharT>>(is.getloc());
        std::tm tm{};
#endif
        const CharT *command = nullptr;
        auto modified = CharT{};
        auto width = -1;

        CONSTDATA int not_a_year = numeric_limits<int>::min();
        CONSTDATA int not_a_2digit_year = 100;
        CONSTDATA int not_a_century = not_a_year / 100;
        CONSTDATA int not_a_month = 0;
        CONSTDATA int not_a_day = 0;
        CONSTDATA int not_a_hour = numeric_limits<int>::min();
        CONSTDATA int not_a_hour_12_value = 0;
        CONSTDATA int not_a_minute = not_a_hour;
        CONSTDATA Duration not_a_second = Duration::min();
        CONSTDATA int not_a_doy = 0;
        CONSTDATA int not_a_weekday = 8;
        CONSTDATA int not_a_week_num = 100;
        CONSTDATA int not_a_ampm = -1;
        CONSTDATA minutes not_a_offset = minutes::min();

        int Y = not_a_year;                                  // c, F, Y                   *
        int y = not_a_2digit_year;                           // D, x, y                   *
        int g = not_a_2digit_year;                           // g                         *
        int G = not_a_year;                                  // G                         *
        int C = not_a_century;                               // C                         *
        int m = not_a_month;                                 // b, B, h, m, c, D, F, x    *
        int d = not_a_day;                                   // c, d, D, e, F, x          *
        int j = not_a_doy;                                   // j                         *
        int wd = not_a_weekday;                              // a, A, u, w                *
        int H = not_a_hour;                                  // c, H, R, T, X             *
        int I = not_a_hour_12_value;                         // I, r                      *
        int p = not_a_ampm;                                  // p, r                      *
        int M = not_a_minute;                                // c, M, r, R, T, X          *
        Duration s = not_a_second;                           // c, r, S, T, X             *
        int U = not_a_week_num;                              // U                         *
        int V = not_a_week_num;                              // V                         *
        int W = not_a_week_num;                              // W                         *
        std::basic_string<CharT, Traits, Alloc> temp_abbrev; // Z   *
        minutes temp_offset = not_a_offset;                  // z                    *

        using detail::checked_set;
        using detail::read;
        using detail::rld;
        using detail::rs;
        using detail::ru;
        for (; *fmt && is.rdstate() == std::ios::goodbit; ++fmt) {
            switch (*fmt) {
                case 'a':
                case 'A':
                case 'u':
                case 'w': // wd:  a, A, u, w
                    if (command) {
                        int trial_wd = not_a_weekday;
                        if (*fmt == 'a' || *fmt == 'A') {
                            if (modified == CharT{}) {
#if !ONLY_C_LOCALE
                                ios_base::iostate err = ios_base::goodbit;
                                f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                                is.setstate(err);
                                if (!is.fail())
                                    trial_wd = tm.tm_wday;
#else
                                auto nm = detail::weekday_names();
                                auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                                if (!is.fail())
                                    trial_wd = i % 7;
#endif
                            } else
                                read(is, CharT{'%'}, width, modified, *fmt);
                        } else // *fmt == 'u' || *fmt == 'w'
                        {
#if !ONLY_C_LOCALE
                            if (modified == CharT{})
#else
                            if (modified != CharT{'E'})
#endif
                            {
                                read(is, ru{trial_wd, 1, width == -1 ? 1u : static_cast<unsigned>(width)});
                                if (!is.fail()) {
                                    if (*fmt == 'u') {
                                        if (!(1 <= trial_wd && trial_wd <= 7)) {
                                            trial_wd = not_a_weekday;
                                            is.setstate(ios_base::failbit);
                                        } else if (trial_wd == 7)
                                            trial_wd = 0;
                                    } else // *fmt == 'w'
                                    {
                                        if (!(0 <= trial_wd && trial_wd <= 6)) {
                                            trial_wd = not_a_weekday;
                                            is.setstate(ios_base::failbit);
                                        }
                                    }
                                }
                            }
#if !ONLY_C_LOCALE
                            else if (modified == CharT{'O'}) {
                                ios_base::iostate err = ios_base::goodbit;
                                f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                                is.setstate(err);
                                if (!is.fail())
                                    trial_wd = tm.tm_wday;
                            }
#endif
                            else
                                read(is, CharT{'%'}, width, modified, *fmt);
                        }
                        if (trial_wd != not_a_weekday)
                            checked_set(wd, trial_wd, not_a_weekday, is);
                    } else // !command
                        read(is, *fmt);
                    command = nullptr;
                    width = -1;
                    modified = CharT{};
                    break;
                case 'b':
                case 'B':
                case 'h':
                    if (command) {
                        if (modified == CharT{}) {
                            int ttm = not_a_month;
#if !ONLY_C_LOCALE
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                ttm = tm.tm_mon + 1;
                            is.setstate(err);
#else
                            auto nm = detail::month_names();
                            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                            if (!is.fail())
                                ttm = i % 12 + 1;
#endif
                            checked_set(m, ttm, not_a_month, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'c':
                    if (command) {
                        if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0) {
                                checked_set(Y, tm.tm_year + 1900, not_a_year, is);
                                checked_set(m, tm.tm_mon + 1, not_a_month, is);
                                checked_set(d, tm.tm_mday, not_a_day, is);
                                checked_set(H, tm.tm_hour, not_a_hour, is);
                                checked_set(M, tm.tm_min, not_a_minute, is);
                                checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                                            not_a_second, is);
                            }
                            is.setstate(err);
#else
                            // "%a %b %e %T %Y"
                            auto nm = detail::weekday_names();
                            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                            checked_set(wd, static_cast<int>(i % 7), not_a_weekday, is);
                            ws(is);
                            nm = detail::month_names();
                            i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                            checked_set(m, static_cast<int>(i % 12 + 1), not_a_month, is);
                            ws(is);
                            int td = not_a_day;
                            read(is, rs{td, 1, 2});
                            checked_set(d, td, not_a_day, is);
                            ws(is);
                            using dfs = detail::decimal_format_seconds<Duration>;
                            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
                            int tH;
                            int tM;
                            long double S;
                            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                                 CharT{':'}, rld{S, 1, w});
                            checked_set(H, tH, not_a_hour, is);
                            checked_set(M, tM, not_a_minute, is);
                            checked_set(s, round<Duration>(duration<long double>{S}),
                                        not_a_second, is);
                            ws(is);
                            int tY = not_a_year;
                            read(is, rs{tY, 1, 4u});
                            checked_set(Y, tY, not_a_year, is);
#endif
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'x':
                    if (command) {
                        if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0) {
                                checked_set(Y, tm.tm_year + 1900, not_a_year, is);
                                checked_set(m, tm.tm_mon + 1, not_a_month, is);
                                checked_set(d, tm.tm_mday, not_a_day, is);
                            }
                            is.setstate(err);
#else
                            // "%m/%d/%y"
                            int ty = not_a_2digit_year;
                            int tm = not_a_month;
                            int td = not_a_day;
                            read(is, ru{tm, 1, 2}, CharT{'/'}, ru{td, 1, 2}, CharT{'/'},
                                 rs{ty, 1, 2});
                            checked_set(y, ty, not_a_2digit_year, is);
                            checked_set(m, tm, not_a_month, is);
                            checked_set(d, td, not_a_day, is);
#endif
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'X':
                    if (command) {
                        if (modified != CharT{'O'}) {
#if !ONLY_C_LOCALE
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0) {
                                checked_set(H, tm.tm_hour, not_a_hour, is);
                                checked_set(M, tm.tm_min, not_a_minute, is);
                                checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                                            not_a_second, is);
                            }
                            is.setstate(err);
#else
                            // "%T"
                            using dfs = detail::decimal_format_seconds<Duration>;
                            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
                            int tH = not_a_hour;
                            int tM = not_a_minute;
                            long double S;
                            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                                 CharT{':'}, rld{S, 1, w});
                            checked_set(H, tH, not_a_hour, is);
                            checked_set(M, tM, not_a_minute, is);
                            checked_set(s, round<Duration>(duration<long double>{S}),
                                        not_a_second, is);
#endif
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'C':
                    if (command) {
                        int tC = not_a_century;
#if !ONLY_C_LOCALE
                        if (modified == CharT{}) {
#endif
                            read(is, rs{tC, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
#if !ONLY_C_LOCALE
                        } else {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0) {
                                auto tY = tm.tm_year + 1900;
                                tC = (tY >= 0 ? tY : tY - 99) / 100;
                            }
                            is.setstate(err);
                        }
#endif
                        checked_set(C, tC, not_a_century, is);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'D':
                    if (command) {
                        if (modified == CharT{}) {
                            int tn = not_a_month;
                            int td = not_a_day;
                            int ty = not_a_2digit_year;
                            read(is, ru{tn, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
                                 ru{td, 1, 2}, CharT{'\0'}, CharT{'/'}, CharT{'\0'},
                                 rs{ty, 1, 2});
                            checked_set(y, ty, not_a_2digit_year, is);
                            checked_set(m, tn, not_a_month, is);
                            checked_set(d, td, not_a_day, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'F':
                    if (command) {
                        if (modified == CharT{}) {
                            int tY = not_a_year;
                            int tn = not_a_month;
                            int td = not_a_day;
                            read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)},
                                 CharT{'-'}, ru{tn, 1, 2}, CharT{'-'}, ru{td, 1, 2});
                            checked_set(Y, tY, not_a_year, is);
                            checked_set(m, tn, not_a_month, is);
                            checked_set(d, td, not_a_day, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'd':
                case 'e':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'E'})
#endif
                        {
                            int td = not_a_day;
                            read(is, rs{td, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(d, td, not_a_day, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            command = nullptr;
                            width = -1;
                            modified = CharT{};
                            if ((err & ios::failbit) == 0)
                                checked_set(d, tm.tm_mday, not_a_day, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'H':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'E'})
#endif
                        {
                            int tH = not_a_hour;
                            read(is, ru{tH, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(H, tH, not_a_hour, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(H, tm.tm_hour, not_a_hour, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'I':
                    if (command) {
                        if (modified == CharT{}) {
                            int tI = not_a_hour_12_value;
                            // reads in an hour into I, but most be in [1, 12]
                            read(is, rs{tI, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            if (!(1 <= tI && tI <= 12))
                                is.setstate(ios::failbit);
                            checked_set(I, tI, not_a_hour_12_value, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'j':
                    if (command) {
                        if (modified == CharT{}) {
                            int tj = not_a_doy;
                            read(is, ru{tj, 1, width == -1 ? 3u : static_cast<unsigned>(width)});
                            checked_set(j, tj, not_a_doy, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'M':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'E'})
#endif
                        {
                            int tM = not_a_minute;
                            read(is, ru{tM, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(M, tM, not_a_minute, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(M, tm.tm_min, not_a_minute, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'm':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'E'})
#endif
                        {
                            int tn = not_a_month;
                            read(is, rs{tn, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(m, tn, not_a_month, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(m, tm.tm_mon + 1, not_a_month, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'n':
                case 't':
                    if (command) {
                        if (modified == CharT{}) {
                            // %n matches a single white space character
                            // %t matches 0 or 1 white space characters
                            auto ic = is.peek();
                            if (Traits::eq_int_type(ic, Traits::eof())) {
                                ios_base::iostate err = ios_base::eofbit;
                                if (*fmt == 'n')
                                    err |= ios_base::failbit;
                                is.setstate(err);
                                break;
                            }
                            if (isspace(ic)) {
                                (void) is.get();
                            } else if (*fmt == 'n')
                                is.setstate(ios_base::failbit);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'p':
                    if (command) {
                        if (modified == CharT{}) {
                            int tp = not_a_ampm;
#if !ONLY_C_LOCALE
                            tm = std::tm{};
                            tm.tm_hour = 1;
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            is.setstate(err);
                            if (tm.tm_hour == 1)
                                tp = 0;
                            else if (tm.tm_hour == 13)
                                tp = 1;
                            else
                                is.setstate(err);
#else
                            auto nm = detail::ampm_names();
                            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                            tp = i;
#endif
                            checked_set(p, tp, not_a_ampm, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);

                    break;
                case 'r':
                    if (command) {
                        if (modified == CharT{}) {
#if !ONLY_C_LOCALE
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0) {
                                checked_set(H, tm.tm_hour, not_a_hour, is);
                                checked_set(M, tm.tm_min, not_a_hour, is);
                                checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                                            not_a_second, is);
                            }
                            is.setstate(err);
#else
                            // "%I:%M:%S %p"
                            using dfs = detail::decimal_format_seconds<Duration>;
                            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
                            long double S;
                            int tI = not_a_hour_12_value;
                            int tM = not_a_minute;
                            read(is, ru{tI, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                                 CharT{':'}, rld{S, 1, w});
                            checked_set(I, tI, not_a_hour_12_value, is);
                            checked_set(M, tM, not_a_minute, is);
                            checked_set(s, round<Duration>(duration<long double>{S}),
                                        not_a_second, is);
                            ws(is);
                            auto nm = detail::ampm_names();
                            auto i = detail::scan_keyword(is, nm.first, nm.second) - nm.first;
                            checked_set(p, static_cast<int>(i), not_a_ampm, is);
#endif
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'R':
                    if (command) {
                        if (modified == CharT{}) {
                            int tH = not_a_hour;
                            int tM = not_a_minute;
                            read(is, ru{tH, 1, 2}, CharT{'\0'}, CharT{':'}, CharT{'\0'},
                                 ru{tM, 1, 2}, CharT{'\0'});
                            checked_set(H, tH, not_a_hour, is);
                            checked_set(M, tM, not_a_minute, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'S':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'E'})
#endif
                        {
                            using dfs = detail::decimal_format_seconds<Duration>;
                            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
                            long double S;
                            read(is, rld{S, 1, width == -1 ? w : static_cast<unsigned>(width)});
                            checked_set(s, round<Duration>(duration<long double>{S}),
                                        not_a_second, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'O'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(s, duration_cast<Duration>(seconds{tm.tm_sec}),
                                            not_a_second, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'T':
                    if (command) {
                        if (modified == CharT{}) {
                            using dfs = detail::decimal_format_seconds<Duration>;
                            CONSTDATA auto w = Duration::period::den == 1 ? 2 : 3 + dfs::width;
                            int tH = not_a_hour;
                            int tM = not_a_minute;
                            long double S;
                            read(is, ru{tH, 1, 2}, CharT{':'}, ru{tM, 1, 2},
                                 CharT{':'}, rld{S, 1, w});
                            checked_set(H, tH, not_a_hour, is);
                            checked_set(M, tM, not_a_minute, is);
                            checked_set(s, round<Duration>(duration<long double>{S}),
                                        not_a_second, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'Y':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#else
                        if (modified != CharT{'O'})
#endif
                        {
                            int tY = not_a_year;
                            read(is, rs{tY, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
                            checked_set(Y, tY, not_a_year, is);
                        }
#if !ONLY_C_LOCALE
                        else if (modified == CharT{'E'}) {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(Y, tm.tm_year + 1900, not_a_year, is);
                            is.setstate(err);
                        }
#endif
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'y':
                    if (command) {
#if !ONLY_C_LOCALE
                        if (modified == CharT{})
#endif
                        {
                            int ty = not_a_2digit_year;
                            read(is, ru{ty, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(y, ty, not_a_2digit_year, is);
                        }
#if !ONLY_C_LOCALE
                        else {
                            ios_base::iostate err = ios_base::goodbit;
                            f.get(is, nullptr, is, err, &tm, command, fmt + 1);
                            if ((err & ios::failbit) == 0)
                                checked_set(Y, tm.tm_year + 1900, not_a_year, is);
                            is.setstate(err);
                        }
#endif
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'g':
                    if (command) {
                        if (modified == CharT{}) {
                            int tg = not_a_2digit_year;
                            read(is, ru{tg, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(g, tg, not_a_2digit_year, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'G':
                    if (command) {
                        if (modified == CharT{}) {
                            int tG = not_a_year;
                            read(is, rs{tG, 1, width == -1 ? 4u : static_cast<unsigned>(width)});
                            checked_set(G, tG, not_a_year, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'U':
                    if (command) {
                        if (modified == CharT{}) {
                            int tU = not_a_week_num;
                            read(is, ru{tU, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(U, tU, not_a_week_num, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'V':
                    if (command) {
                        if (modified == CharT{}) {
                            int tV = not_a_week_num;
                            read(is, ru{tV, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(V, tV, not_a_week_num, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'W':
                    if (command) {
                        if (modified == CharT{}) {
                            int tW = not_a_week_num;
                            read(is, ru{tW, 1, width == -1 ? 2u : static_cast<unsigned>(width)});
                            checked_set(W, tW, not_a_week_num, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'E':
                case 'O':
                    if (command) {
                        if (modified == CharT{}) {
                            modified = *fmt;
                        } else {
                            read(is, CharT{'%'}, width, modified, *fmt);
                            command = nullptr;
                            width = -1;
                            modified = CharT{};
                        }
                    } else
                        read(is, *fmt);
                    break;
                case '%':
                    if (command) {
                        if (modified == CharT{})
                            read(is, *fmt);
                        else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        command = fmt;
                    break;
                case 'z':
                    if (command) {
                        int tH, tM;
                        minutes toff = not_a_offset;
                        bool neg = false;
                        auto ic = is.peek();
                        if (!Traits::eq_int_type(ic, Traits::eof())) {
                            auto c = static_cast<char>(Traits::to_char_type(ic));
                            if (c == '-')
                                neg = true;
                        }
                        if (modified == CharT{}) {
                            read(is, rs{tH, 2, 2});
                            if (!is.fail())
                                toff = hours{std::abs(tH)};
                            if (is.good()) {
                                ic = is.peek();
                                if (!Traits::eq_int_type(ic, Traits::eof())) {
                                    auto c = static_cast<char>(Traits::to_char_type(ic));
                                    if ('0' <= c && c <= '9') {
                                        read(is, ru{tM, 2, 2});
                                        if (!is.fail())
                                            toff += minutes{tM};
                                    }
                                }
                            }
                        } else {
                            read(is, rs{tH, 1, 2});
                            if (!is.fail())
                                toff = hours{std::abs(tH)};
                            if (is.good()) {
                                ic = is.peek();
                                if (!Traits::eq_int_type(ic, Traits::eof())) {
                                    auto c = static_cast<char>(Traits::to_char_type(ic));
                                    if (c == ':') {
                                        (void) is.get();
                                        read(is, ru{tM, 2, 2});
                                        if (!is.fail())
                                            toff += minutes{tM};
                                    }
                                }
                            }
                        }
                        if (neg)
                            toff = -toff;
                        checked_set(temp_offset, toff, not_a_offset, is);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                case 'Z':
                    if (command) {
                        if (modified == CharT{}) {
                            std::basic_string<CharT, Traits, Alloc> buf;
                            while (is.rdstate() == std::ios::goodbit) {
                                auto i = is.rdbuf()->sgetc();
                                if (Traits::eq_int_type(i, Traits::eof())) {
                                    is.setstate(ios::eofbit);
                                    break;
                                }
                                auto wc = Traits::to_char_type(i);
                                auto c = static_cast<char>(wc);
                                // is c a valid time zone name or abbreviation character?
                                if (!(CharT{1} < wc && wc < CharT{127}) || !(isalnum(c) ||
                                                                             c == '_' || c == '/' || c == '-' || c == '+'))
                                    break;
                                buf.push_back(c);
                                is.rdbuf()->sbumpc();
                            }
                            if (buf.empty())
                                is.setstate(ios::failbit);
                            checked_set(temp_abbrev, buf, {}, is);
                        } else
                            read(is, CharT{'%'}, width, modified, *fmt);
                        command = nullptr;
                        width = -1;
                        modified = CharT{};
                    } else
                        read(is, *fmt);
                    break;
                default:
                    if (command) {
                        if (width == -1 && modified == CharT{} && '0' <= *fmt && *fmt <= '9') {
                            width = static_cast<char>(*fmt) - '0';
                            while ('0' <= fmt[1] && fmt[1] <= '9')
                                width = 10 * width + static_cast<char>(*++fmt) - '0';
                        } else {
                            if (modified == CharT{})
                                read(is, CharT{'%'}, width, *fmt);
                            else
                                read(is, CharT{'%'}, width, modified, *fmt);
                            command = nullptr;
                            width = -1;
                            modified = CharT{};
                        }
                    } else // !command
                    {
                        if (isspace(static_cast<unsigned char>(*fmt)))
                            ws(is); // space matches 0 or more white space characters
                        else
                            read(is, *fmt);
                    }
                    break;
            }
        }
        // is.rdstate() != ios::goodbit || *fmt == CharT{}
        if (is.rdstate() == ios::goodbit && command) {
            if (modified == CharT{})
                read(is, CharT{'%'}, width);
            else
                read(is, CharT{'%'}, width, modified);
        }
        if (is.rdstate() != ios::goodbit && *fmt != CharT{} && !is.fail())
            is.setstate(ios::failbit);
        if (!is.fail()) {
            if (y != not_a_2digit_year) {
                // Convert y and an optional C to Y
                if (!(0 <= y && y <= 99))
                    goto broken;
                if (C == not_a_century) {
                    if (Y == not_a_year) {
                        if (y >= 69)
                            C = 19;
                        else
                            C = 20;
                    } else {
                        C = (Y >= 0 ? Y : Y - 100) / 100;
                    }
                }
                int tY;
                if (C >= 0)
                    tY = 100 * C + y;
                else
                    tY = 100 * (C + 1) - (y == 0 ? 100 : y);
                if (Y != not_a_year && Y != tY)
                    goto broken;
                Y = tY;
            }
            if (g != not_a_2digit_year) {
                // Convert g and an optional C to G
                if (!(0 <= g && g <= 99))
                    goto broken;
                if (C == not_a_century) {
                    if (G == not_a_year) {
                        if (g >= 69)
                            C = 19;
                        else
                            C = 20;
                    } else {
                        C = (G >= 0 ? G : G - 100) / 100;
                    }
                }
                int tG;
                if (C >= 0)
                    tG = 100 * C + g;
                else
                    tG = 100 * (C + 1) - (g == 0 ? 100 : g);
                if (G != not_a_year && G != tG)
                    goto broken;
                G = tG;
            }
            if (Y < static_cast<int>(year::min()) || Y > static_cast<int>(year::max()))
                Y = not_a_year;
            bool computed = false;
            if (G != not_a_year && V != not_a_week_num && wd != not_a_weekday) {
                year_month_day ymd_trial = sys_days(year{G - 1} / December / Thursday[last]) +
                                           (Monday - Thursday) + weeks{V - 1} +
                                           (weekday{static_cast<unsigned>(wd)} - Monday);
                if (Y == not_a_year)
                    Y = static_cast<int>(ymd_trial.year());
                else if (year{Y} != ymd_trial.year())
                    goto broken;
                if (m == not_a_month)
                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
                    goto broken;
                if (d == not_a_day)
                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
                    goto broken;
                computed = true;
            }
            if (Y != not_a_year && U != not_a_week_num && wd != not_a_weekday) {
                year_month_day ymd_trial = sys_days(year{Y} / January / Sunday[1]) +
                                           weeks{U - 1} +
                                           (weekday{static_cast<unsigned>(wd)} - Sunday);
                if (Y == not_a_year)
                    Y = static_cast<int>(ymd_trial.year());
                else if (year{Y} != ymd_trial.year())
                    goto broken;
                if (m == not_a_month)
                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
                    goto broken;
                if (d == not_a_day)
                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
                    goto broken;
                computed = true;
            }
            if (Y != not_a_year && W != not_a_week_num && wd != not_a_weekday) {
                year_month_day ymd_trial = sys_days(year{Y} / January / Monday[1]) +
                                           weeks{W - 1} +
                                           (weekday{static_cast<unsigned>(wd)} - Monday);
                if (Y == not_a_year)
                    Y = static_cast<int>(ymd_trial.year());
                else if (year{Y} != ymd_trial.year())
                    goto broken;
                if (m == not_a_month)
                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
                    goto broken;
                if (d == not_a_day)
                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
                    goto broken;
                computed = true;
            }
            if (j != 0 && Y != not_a_year) {
                auto ymd_trial = year_month_day{local_days(year{Y} / 1 / 1) + days{j - 1}};
                if (m == 0)
                    m = static_cast<int>(static_cast<unsigned>(ymd_trial.month()));
                else if (month(static_cast<unsigned>(m)) != ymd_trial.month())
                    goto broken;
                if (d == 0)
                    d = static_cast<int>(static_cast<unsigned>(ymd_trial.day()));
                else if (day(static_cast<unsigned>(d)) != ymd_trial.day())
                    goto broken;
            }
            auto ymd = year{Y} / m / d;
            if (ymd.ok()) {
                if (wd == not_a_weekday)
                    wd = static_cast<int>((weekday(sys_days(ymd)) - Sunday).count());
                else if (wd != static_cast<int>((weekday(sys_days(ymd)) - Sunday).count()))
                    goto broken;
                if (!computed) {
                    if (G != not_a_year || V != not_a_week_num) {
                        sys_days sd = ymd;
                        auto G_trial = year_month_day{sd + days{3}}.year();
                        auto start = sys_days((G_trial - years{1}) / December / Thursday[last]) +
                                     (Monday - Thursday);
                        if (sd < start) {
                            --G_trial;
                            if (V != not_a_week_num)
                                start = sys_days((G_trial - years{1}) / December / Thursday[last]) + (Monday - Thursday);
                        }
                        if (G != not_a_year && G != static_cast<int>(G_trial))
                            goto broken;
                        if (V != not_a_week_num) {
                            auto V_trial = duration_cast<weeks>(sd - start).count() + 1;
                            if (V != V_trial)
                                goto broken;
                        }
                    }
                    if (U != not_a_week_num) {
                        auto start = sys_days(Sunday[1] / January / ymd.year());
                        auto U_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
                        if (U != U_trial)
                            goto broken;
                    }
                    if (W != not_a_week_num) {
                        auto start = sys_days(Monday[1] / January / ymd.year());
                        auto W_trial = floor<weeks>(sys_days(ymd) - start).count() + 1;
                        if (W != W_trial)
                            goto broken;
                    }
                }
            }
            fds.ymd = ymd;
            if (I != not_a_hour_12_value) {
                if (!(1 <= I && I <= 12))
                    goto broken;
                if (p != not_a_ampm) {
                    // p is in [0, 1] == [AM, PM]
                    // Store trial H in I
                    if (I == 12)
                        --p;
                    I += p * 12;
                    // Either set H from I or make sure H and I are consistent
                    if (H == not_a_hour)
                        H = I;
                    else if (I != H)
                        goto broken;
                } else // p == not_a_ampm
                {
                    // if H, make sure H and I could be consistent
                    if (H != not_a_hour) {
                        if (I == 12) {
                            if (H != 0 && H != 12)
                                goto broken;
                        } else if (!(I == H || I == H + 12)) {
                            goto broken;
                        }
                    }
                }
            }
            if (H != not_a_hour) {
                fds.has_tod = true;
                fds.tod = time_of_day<Duration>{hours{H}};
            }
            if (M != not_a_minute) {
                fds.has_tod = true;
                fds.tod.m_ = minutes{M};
            }
            if (s != not_a_second) {
                fds.has_tod = true;
                fds.tod.s_ = detail::decimal_format_seconds<Duration>{s};
            }
            if (wd != not_a_weekday)
                fds.wd = weekday{static_cast<unsigned>(wd)};
            if (abbrev != nullptr)
                *abbrev = std::move(temp_abbrev);
            if (offset != nullptr && temp_offset != not_a_offset)
                *offset = temp_offset;
        }
        return is;
    }
broken:
    is.setstate(ios_base::failbit);
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, year &y,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.year().ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        y = fds.ymd.year();
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, month &m,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.month().ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        m = fds.ymd.month();
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, day &d,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.day().ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        d = fds.ymd.day();
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, weekday &wd,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.wd.ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        wd = fds.wd;
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, year_month &ym,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.month().ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        ym = fds.ymd.year() / fds.ymd.month();
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt, month_day &md,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.month().ok() || !fds.ymd.day().ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        md = fds.ymd.month() / fds.ymd.day();
    return is;
}

template <class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            year_month_day &ymd, std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = seconds;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.ok())
        is.setstate(ios::failbit);
    if (!is.fail())
        ymd = fds.ymd;
    return is;
}

template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            sys_time<Duration> &tp, std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = typename common_type<Duration, seconds>::type;
    minutes offset_local{};
    auto offptr = offset ? offset : &offset_local;
    fields<CT> fds{};
    fds.has_tod = true;
    from_stream(is, fmt, fds, abbrev, offptr);
    if (!fds.ymd.ok() || !fds.tod.in_conventional_range())
        is.setstate(ios::failbit);
    if (!is.fail())
        tp = round<Duration>(sys_days(fds.ymd) - *offptr + fds.tod.to_duration());
    return is;
}

template <class Duration, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            local_time<Duration> &tp, std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using CT = typename common_type<Duration, seconds>::type;
    fields<CT> fds{};
    fds.has_tod = true;
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.ymd.ok() || !fds.tod.in_conventional_range())
        is.setstate(ios::failbit);
    if (!is.fail())
        tp = round<Duration>(local_seconds{local_days(fds.ymd)} + fds.tod.to_duration());
    return is;
}

template <class Rep, class Period, class CharT, class Traits, class Alloc = std::allocator<CharT>>
std::basic_istream<CharT, Traits> &
from_stream(std::basic_istream<CharT, Traits> &is, const CharT *fmt,
            std::chrono::duration<Rep, Period> &d,
            std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
            std::chrono::minutes *offset = nullptr) {
    using namespace std;
    using namespace std::chrono;
    using Duration = std::chrono::duration<Rep, Period>;
    using CT = typename common_type<Duration, seconds>::type;
    fields<CT> fds{};
    from_stream(is, fmt, fds, abbrev, offset);
    if (!fds.has_tod)
        is.setstate(ios::failbit);
    if (!is.fail())
        d = duration_cast<Duration>(fds.tod.to_duration());
    return is;
}

template <class Parsable, class CharT, class Traits = std::char_traits<CharT>,
          class Alloc = std::allocator<CharT>>
struct parse_manip {
    const std::basic_string<CharT, Traits, Alloc> format_;
    Parsable &tp_;
    std::basic_string<CharT, Traits, Alloc> *abbrev_;
    std::chrono::minutes *offset_;

  public:
    parse_manip(std::basic_string<CharT, Traits, Alloc> format, Parsable &tp,
                std::basic_string<CharT, Traits, Alloc> *abbrev = nullptr,
                std::chrono::minutes *offset = nullptr)
        : format_(std::move(format)), tp_(tp), abbrev_(abbrev), offset_(offset) {}
};

template <class Parsable, class CharT, class Traits, class Alloc>
std::basic_istream<CharT, Traits> &
operator>>(std::basic_istream<CharT, Traits> &is,
           const parse_manip<Parsable, CharT, Traits, Alloc> &x) {
    return from_stream(is, x.format_.c_str(), x.tp_, x.abbrev_, x.offset_);
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(),
                            format.c_str(), tp),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp}) {
    return {format, tp};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(),
                            format.c_str(), tp, &abbrev),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev}) {
    return {format, tp, &abbrev};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::chrono::minutes &offset)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(),
                            format.c_str(), tp,
                            std::declval<std::basic_string<CharT, Traits, Alloc> *>(),
                            &offset),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, nullptr, &offset}) {
    return {format, tp, nullptr, &offset};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const std::basic_string<CharT, Traits, Alloc> &format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev, std::chrono::minutes &offset)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(),
                            format.c_str(), tp, &abbrev, &offset),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev, &offset}) {
    return {format, tp, &abbrev, &offset};
}

// const CharT* formats

template <class Parsable, class CharT>
inline auto
parse(const CharT *format, Parsable &tp)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT> &>(), format, tp),
                parse_manip<Parsable, CharT>{format, tp}) {
    return {format, tp};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const CharT *format, Parsable &tp, std::basic_string<CharT, Traits, Alloc> &abbrev)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(), format,
                            tp, &abbrev),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev}) {
    return {format, tp, &abbrev};
}

template <class Parsable, class CharT>
inline auto
parse(const CharT *format, Parsable &tp, std::chrono::minutes &offset)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT> &>(), format,
                            tp, std::declval<std::basic_string<CharT> *>(), &offset),
                parse_manip<Parsable, CharT>{format, tp, nullptr, &offset}) {
    return {format, tp, nullptr, &offset};
}

template <class Parsable, class CharT, class Traits, class Alloc>
inline auto
parse(const CharT *format, Parsable &tp,
      std::basic_string<CharT, Traits, Alloc> &abbrev, std::chrono::minutes &offset)
    -> decltype(from_stream(std::declval<std::basic_istream<CharT, Traits> &>(), format,
                            tp, &abbrev, &offset),
                parse_manip<Parsable, CharT, Traits, Alloc>{format, tp, &abbrev, &offset}) {
    return {format, tp, &abbrev, &offset};
}

// duration streaming

namespace detail {

template <class CharT, std::size_t N>
class string_literal;

template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
inline CONSTCD14
    string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
                   N1 + N2 - 1>
    operator+(const string_literal<CharT1, N1> &x, const string_literal<CharT2, N2> &y) NOEXCEPT;

template <class CharT, std::size_t N>
class string_literal {
    CharT p_[N];

    CONSTCD11 string_literal() NOEXCEPT
        : p_{} {}

  public:
    using const_iterator = const CharT *;

    string_literal(string_literal const &) = default;
    string_literal &operator=(string_literal const &) = delete;

    template <std::size_t N1 = 2,
              class = typename std::enable_if<N1 == N>::type>
    CONSTCD11 string_literal(CharT c) NOEXCEPT
        : p_{c} {
    }

    template <std::size_t N1 = 3,
              class = typename std::enable_if<N1 == N>::type>
    CONSTCD11 string_literal(CharT c1, CharT c2) NOEXCEPT
        : p_{c1, c2} {
    }

    template <std::size_t N1 = 4,
              class = typename std::enable_if<N1 == N>::type>
    CONSTCD11 string_literal(CharT c1, CharT c2, CharT c3) NOEXCEPT
        : p_{c1, c2, c3} {
    }

    CONSTCD14 string_literal(const CharT (&a)[N]) NOEXCEPT
        : p_{} {
        for (std::size_t i = 0; i < N; ++i)
            p_[i] = a[i];
    }

    template <class U = CharT,
              class = typename std::enable_if<(1 < sizeof(U))>::type>
    CONSTCD14 string_literal(const char (&a)[N]) NOEXCEPT
        : p_{} {
        for (std::size_t i = 0; i < N; ++i)
            p_[i] = a[i];
    }

    template <class CharT2,
              class = typename std::enable_if<!std::is_same<CharT2, CharT>::value>::type>
    CONSTCD14 string_literal(string_literal<CharT2, N> const &a) NOEXCEPT
        : p_{} {
        for (std::size_t i = 0; i < N; ++i)
            p_[i] = a[i];
    }

    CONSTCD11 const CharT *data() const NOEXCEPT { return p_; }
    CONSTCD11 std::size_t size() const NOEXCEPT { return N - 1; }

    CONSTCD11 const_iterator begin() const NOEXCEPT { return p_; }
    CONSTCD11 const_iterator end() const NOEXCEPT { return p_ + N - 1; }

    CONSTCD11 CharT const &operator[](std::size_t n) const NOEXCEPT {
        return p_[n];
    }

    template <class Traits>
    friend std::basic_ostream<CharT, Traits> &
    operator<<(std::basic_ostream<CharT, Traits> &os, const string_literal &s) {
        return os << s.p_;
    }

    template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
    friend CONSTCD14
        string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
                       N1 + N2 - 1>
        operator+(const string_literal<CharT1, N1> &x, const string_literal<CharT2, N2> &y) NOEXCEPT;
};

template <class CharT>
CONSTCD11 inline string_literal<CharT, 3>
operator+(const string_literal<CharT, 2> &x, const string_literal<CharT, 2> &y) NOEXCEPT {
    return string_literal<CharT, 3>(x[0], y[0]);
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 4>
operator+(const string_literal<CharT, 3> &x, const string_literal<CharT, 2> &y) NOEXCEPT {
    return string_literal<CharT, 4>(x[0], x[1], y[0]);
}

template <class CharT1, class CharT2, std::size_t N1, std::size_t N2>
CONSTCD14 inline string_literal<typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type,
                                N1 + N2 - 1>
operator+(const string_literal<CharT1, N1> &x, const string_literal<CharT2, N2> &y) NOEXCEPT {
    using CT = typename std::conditional<sizeof(CharT2) <= sizeof(CharT1), CharT1, CharT2>::type;

    string_literal<CT, N1 + N2 - 1> r;
    std::size_t i = 0;
    for (; i < N1 - 1; ++i)
        r.p_[i] = CT(x.p_[i]);
    for (std::size_t j = 0; j < N2; ++j, ++i)
        r.p_[i] = CT(y.p_[j]);

    return r;
}

template <class CharT, class Traits, class Alloc, std::size_t N>
inline std::basic_string<CharT, Traits, Alloc>
operator+(std::basic_string<CharT, Traits, Alloc> x, const string_literal<CharT, N> &y) {
    x.append(y.data(), y.size());
    return x;
}

#if __cplusplus >= 201402 && (!defined(__EDG_VERSION__) || __EDG_VERSION__ > 411) && (!defined(__SUNPRO_CC) || __SUNPRO_CC > 0x5150)

template <class CharT,
          class = std::enable_if_t<std::is_same<CharT, char>{} ||
                                   std::is_same<CharT, wchar_t>{} ||
                                   std::is_same<CharT, char16_t>{} ||
                                   std::is_same<CharT, char32_t>{}>>
CONSTCD14 inline string_literal<CharT, 2>
msl(CharT c) NOEXCEPT {
    return string_literal<CharT, 2>{c};
}

CONSTCD14
inline std::size_t
to_string_len(std::intmax_t i) {
    std::size_t r = 0;
    do {
        i /= 10;
        ++r;
    } while (i > 0);
    return r;
}

template <std::intmax_t N>
    CONSTCD14 inline std::enable_if_t <
    N<10,
      string_literal<char, to_string_len(N) + 1>>
    msl() NOEXCEPT {
    return msl(char(N % 10 + '0'));
}

template <std::intmax_t N>
CONSTCD14 inline std::enable_if_t<
    10 <= N,
    string_literal<char, to_string_len(N) + 1>>
msl() NOEXCEPT {
    return msl<N / 10>() + msl(char(N % 10 + '0'));
}

template <class CharT, std::intmax_t N, std::intmax_t D>
CONSTCD14 inline std::enable_if_t<
    std::ratio<N, D>::type::den != 1,
    string_literal<CharT, to_string_len(std::ratio<N, D>::type::num) +
                              to_string_len(std::ratio<N, D>::type::den) + 4>>
msl(std::ratio<N, D>) NOEXCEPT {
    using R = typename std::ratio<N, D>::type;
    return msl(CharT{'['}) + msl<R::num>() + msl(CharT{'/'}) +
           msl<R::den>() + msl(CharT{']'});
}

template <class CharT, std::intmax_t N, std::intmax_t D>
CONSTCD14 inline std::enable_if_t<
    std::ratio<N, D>::type::den == 1,
    string_literal<CharT, to_string_len(std::ratio<N, D>::type::num) + 3>>
msl(std::ratio<N, D>) NOEXCEPT {
    using R = typename std::ratio<N, D>::type;
    return msl(CharT{'['}) + msl<R::num>() + msl(CharT{']'});
}

#else // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)

inline std::string
to_string(std::uint64_t x) {
    return std::to_string(x);
}

template <class CharT>
inline std::basic_string<CharT>
to_string(std::uint64_t x) {
    auto y = std::to_string(x);
    return std::basic_string<CharT>(y.begin(), y.end());
}

template <class CharT, std::intmax_t N, std::intmax_t D>
inline
    typename std::enable_if<
        std::ratio<N, D>::type::den != 1,
        std::basic_string<CharT>>::type
    msl(std::ratio<N, D>) {
    using R = typename std::ratio<N, D>::type;
    return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{'/'} +
           to_string<CharT>(R::den) + CharT{']'};
}

template <class CharT, std::intmax_t N, std::intmax_t D>
inline
    typename std::enable_if<
        std::ratio<N, D>::type::den == 1,
        std::basic_string<CharT>>::type
    msl(std::ratio<N, D>) {
    using R = typename std::ratio<N, D>::type;
    return std::basic_string<CharT>(1, '[') + to_string<CharT>(R::num) + CharT{']'};
}

#endif // __cplusplus < 201402 || (defined(__EDG_VERSION__) && __EDG_VERSION__ <= 411)

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::atto) NOEXCEPT {
    return string_literal<CharT, 2>{'a'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::femto) NOEXCEPT {
    return string_literal<CharT, 2>{'f'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::pico) NOEXCEPT {
    return string_literal<CharT, 2>{'p'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::nano) NOEXCEPT {
    return string_literal<CharT, 2>{'n'};
}

template <class CharT>
CONSTCD11 inline
    typename std::enable_if<
        std::is_same<CharT, char>::value,
        string_literal<char, 3>>::type
    msl(std::micro) NOEXCEPT {
    return string_literal<char, 3>{'\xC2', '\xB5'};
}

template <class CharT>
CONSTCD11 inline
    typename std::enable_if<
        !std::is_same<CharT, char>::value,
        string_literal<CharT, 2>>::type
    msl(std::micro) NOEXCEPT {
    return string_literal<CharT, 2>{CharT{static_cast<unsigned char>('\xB5')}};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::milli) NOEXCEPT {
    return string_literal<CharT, 2>{'m'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::centi) NOEXCEPT {
    return string_literal<CharT, 2>{'c'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 3>
msl(std::deca) NOEXCEPT {
    return string_literal<CharT, 3>{'d', 'a'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::deci) NOEXCEPT {
    return string_literal<CharT, 2>{'d'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::hecto) NOEXCEPT {
    return string_literal<CharT, 2>{'h'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::kilo) NOEXCEPT {
    return string_literal<CharT, 2>{'k'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::mega) NOEXCEPT {
    return string_literal<CharT, 2>{'M'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::giga) NOEXCEPT {
    return string_literal<CharT, 2>{'G'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::tera) NOEXCEPT {
    return string_literal<CharT, 2>{'T'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::peta) NOEXCEPT {
    return string_literal<CharT, 2>{'P'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
msl(std::exa) NOEXCEPT {
    return string_literal<CharT, 2>{'E'};
}

template <class CharT, class Period>
CONSTCD11 inline auto
get_units(Period p)
    -> decltype(msl<CharT>(p) + string_literal<CharT, 2>{'s'}) {
    return msl<CharT>(p) + string_literal<CharT, 2>{'s'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
get_units(std::ratio<1>) {
    return string_literal<CharT, 2>{'s'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
get_units(std::ratio<3600>) {
    return string_literal<CharT, 2>{'h'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 4>
get_units(std::ratio<60>) {
    return string_literal<CharT, 4>{'m', 'i', 'n'};
}

template <class CharT>
CONSTCD11 inline string_literal<CharT, 2>
get_units(std::ratio<86400>) {
    return string_literal<CharT, 2>{'d'};
}

template <class CharT, class Traits = std::char_traits<CharT>>
struct make_string;

template <>
struct make_string<char> {
    template <class Rep>
    static std::string
    from(Rep n) {
        return std::to_string(n);
    }
};

template <class Traits>
struct make_string<char, Traits> {
    template <class Rep>
    static std::basic_string<char, Traits>
    from(Rep n) {
        auto s = std::to_string(n);
        return std::basic_string<char, Traits>(s.begin(), s.end());
    }
};

template <>
struct make_string<wchar_t> {
    template <class Rep>
    static std::wstring
    from(Rep n) {
        return std::to_wstring(n);
    }
};

template <class Traits>
struct make_string<wchar_t, Traits> {
    template <class Rep>
    static std::basic_string<wchar_t, Traits>
    from(Rep n) {
        auto s = std::to_wstring(n);
        return std::basic_string<wchar_t, Traits>(s.begin(), s.end());
    }
};

} // namespace detail

template <class CharT, class Traits, class Rep, class Period>
inline std::basic_ostream<CharT, Traits> &
operator<<(std::basic_ostream<CharT, Traits> &os,
           const std::chrono::duration<Rep, Period> &d) {
    using namespace detail;
    return os << make_string<CharT, Traits>::from(d.count()) +
                     get_units<CharT>(typename Period::type{});
}

} // namespace date

#ifdef __GNUC__
#pragma GCC diagnostic pop
#endif

#endif // DATE_H
